{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-97200", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-10-26T05:15:01.465Z", "datePublished": "2026-10-26T13:49:40.392Z", "dateUpdated": "2026-10-26T13:49:40.392Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["hackney_conn", "hackney"], "packageName": "hackney", "packageURL": "pkg:hex/hackney", "product": "hackney", "programFiles": ["src/hackney_conn.erl", "src/hackney.erl"], "programRoutines": [{"name": "hackney_conn:read_full_body/2"}, {"name": "hackney_conn:maybe_decompress_body/2"}, {"name": "hackney_conn:decompress_gzip/1"}, {"name": "hackney_conn:decompress_deflate/1"}, {"name": "hackney:request/5"}, {"name": "hackney:body/1"}], "repo": "https://github.com/benoitc/hackney", "vendor": "benoitc", "versions": [{"lessThan": "4.9.0", "status": "affected", "version": "2.0.0-beta.1", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["hackney_conn", "hackney"], "packageName": "benoitc/hackney", "packageURL": "pkg:github/benoitc/hackney", "product": "hackney", "programFiles": ["src/hackney_conn.erl", "src/hackney.erl"], "programRoutines": [{"name": "hackney_conn:read_full_body/2"}, {"name": "hackney_conn:maybe_decompress_body/2"}, {"name": "hackney_conn:decompress_gzip/1"}, {"name": "hackney_conn:decompress_deflate/1"}, {"name": "hackney:request/5"}, {"name": "hackney:body/1"}], "repo": "https://github.com/benoitc/hackney", "vendor": "benoitc", "versions": [{"lessThan": "493e8bf83a391548e5101792276ab3fc428fa76c", "status": "affected", "version": "dc41b79339ca0c41e16d3f2dd17172bc2de855d6", "versionType": "git"}]}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*", "versionEndExcluding": "4.9.0", "versionStartIncluding": "2.0.0-beta.1", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "finder", "value": "Martin Karrer"}, {"lang": "en", "type": "finder", "value": "Quinn Wilton"}, {"lang": "en", "type": "reporter", "value": "Quinn Wilton"}, {"lang": "en", "type": "remediation developer", "value": "Martin Karrer"}, {"lang": "en", "type": "remediation developer", "value": "Benoit Chesneau"}, {"lang": "en", "type": "coordinator", "value": "Jonatan M\u00e4nnchen / EEF"}], "dateAssigned": "2026-10-26T09:42:31.000Z", "datePublic": "2026-10-25T00:00:00.000Z", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Allocation of Resources Without Limits or Throttling vulnerability in <code>hackney_conn</code> in benoitc hackney allows a malicious HTTP server to exhaust client memory via an oversized or highly compressed response body. <code>hackney:request/5</code> and <code>hackney:body/1</code> return the whole response body, and nothing bounds how much the connection process buffers. Any server the client requests can trigger it.</p>\n<p><code>hackney_conn:read_full_body/2</code> and the HTTP/2 and HTTP/3 accumulators append every chunk until the body ends. With <code>{auto_decompress, true}</code> the buffered body is then inflated in one step with <code>zlib:gunzip/1</code> or <code>zlib:inflate/2</code>, which return the whole output at once.</p>\n<p>This issue affects hackney: from 2.0.0-beta.1 before 4.9.0.</p>"}, {"base64": false, "type": "text/markdown", "value": "Allocation of Resources Without Limits or Throttling vulnerability in `hackney_conn` in benoitc hackney allows a malicious HTTP server to exhaust client memory via an oversized or highly compressed response body. `hackney:request/5` and `hackney:body/1` return the whole response body, and nothing bounds how much the connection process buffers. Any server the client requests can trigger it.\n\n`hackney_conn:read_full_body/2` and the HTTP/2 and HTTP/3 accumulators append every chunk until the body ends. With `{auto_decompress, true}` the buffered body is then inflated in one step with `zlib:gunzip/1` or `zlib:inflate/2`, which return the whole output at once.\n\nThis issue affects hackney: from 2.0.0-beta.1 before 4.9.0."}], "value": "Allocation of Resources Without Limits or Throttling vulnerability in hackney_conn in benoitc hackney allows a malicious HTTP server to exhaust client memory via an oversized or highly compressed response body. hackney:request/5 and hackney:body/1 return the whole response body, and nothing bounds how much the connection process buffers. Any server the client requests can trigger it.\n\nhackney_conn:read_full_body/2 and the HTTP/2 and HTTP/3 accumulators append every chunk until the body ends. With {auto_decompress, true} the buffered body is then inflated in one step with zlib:gunzip/1 or zlib:inflate/2, which return the whole output at once.\n\nThis issue affects hackney: from 2.0.0-beta.1 before 4.9.0."}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>A server the client requests can make the client allocate memory proportional to the body it sends, or to its decompressed size, until the node runs out of memory.</p>"}, {"base64": false, "type": "text/markdown", "value": "A server the client requests can make the client allocate memory proportional to the body it sends, or to its decompressed size, until the node runs out of memory."}], "value": "A server the client requests can make the client allocate memory proportional to the body it sends, or to its decompressed size, until the node runs out of memory."}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 8.2, "baseSeverity": "HIGH", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-409", "description": "CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)", "lang": "en", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-770", "description": "CWE-770 Allocation of Resources Without Limits or Throttling", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-10-26T13:49:40.392Z"}, "references": [{"name": "hackney 4.9.0 release notes", "tags": ["vendor-advisory", "related"], "url": "https://github.com/benoitc/hackney/releases/tag/4.9.0"}, {"name": "EEF CNA record for CVE-2026-97200", "tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-97200.html"}, {"name": "OSV record EEF-CVE-2026-97200", "tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-97200"}, {"name": "Cap buffered response bodies with max_body_size and bound decompression (benoitc/hackney#980)", "tags": ["related"], "url": "https://github.com/benoitc/hackney/pull/980"}, {"name": "Introducing commit dc41b79 in benoitc/hackney", "tags": ["related"], "url": "https://github.com/benoitc/hackney/commit/dc41b79339ca0c41e16d3f2dd17172bc2de855d6"}, {"name": "Fix commit 493e8bf in benoitc/hackney", "tags": ["patch"], "url": "https://github.com/benoitc/hackney/commit/493e8bf83a391548e5101792276ab3fc428fa76c"}], "source": {"discovery": "EXTERNAL"}, "title": "Unbounded response body buffering and decompression in hackney", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Leave <code>auto_decompress</code> disabled (the default). Without it <code>hackney_conn:maybe_decompress_body/2</code> never inflates the body, which closes the amplification half. The uncapped raw body read has no workaround.</p>"}, {"base64": false, "type": "text/markdown", "value": "Leave `auto_decompress` disabled (the default). Without it `hackney_conn:maybe_decompress_body/2` never inflates the body, which closes the amplification half. The uncapped raw body read has no workaround."}], "value": "Leave auto_decompress disabled (the default). Without it hackney_conn:maybe_decompress_body/2 never inflates the body, which closes the amplification half. The uncapped raw body read has no workaround."}], "x_proofOfConcept": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<ol>\n<li>Build a gzip stream whose inflated size is 1 GB from a reused 64 KB chunk of zero bytes (deflate with window bits 31, best compression). The stream is about 1 MB on the wire.</li>\n<li>Start a TCP listener on loopback that accepts one connection, reads the request, and answers <code>HTTP/1.1 200 OK</code> with <code>Content-Encoding: gzip</code>, a <code>Content-Length</code> matching the stream, <code>Connection: close</code>, and the stream as body.</li>\n<li>From a node running a vulnerable hackney, call <code>hackney:request(get, Url, [], &lt;&lt;&gt;&gt;, [{auto_decompress, true}, with_body])</code> against that listener.</li>\n<li>Observe the returned body of 1,048,576,000 bytes and the VM memory growing by about 1.8 GB for a 1,019,197 byte response. A larger stream, or an endless body without <code>auto_decompress</code>, drives the node out of memory.</li>\n</ol>"}, {"base64": false, "type": "text/markdown", "value": "1. Build a gzip stream whose inflated size is 1 GB from a reused 64 KB chunk of zero bytes (deflate with window bits 31, best compression). The stream is about 1 MB on the wire.\n2. Start a TCP listener on loopback that accepts one connection, reads the request, and answers `HTTP/1.1 200 OK` with `Content-Encoding: gzip`, a `Content-Length` matching the stream, `Connection: close`, and the stream as body.\n3. From a node running a vulnerable hackney, call `hackney:request(get, Url, [], <<>>, [{auto_decompress, true}, with_body])` against that listener.\n4. Observe the returned body of 1,048,576,000 bytes and the VM memory growing by about 1.8 GB for a 1,019,197 byte response. A larger stream, or an endless body without `auto_decompress`, drives the node out of memory."}], "value": "* Build a gzip stream whose inflated size is 1 GB from a reused 64 KB chunk of zero bytes (deflate with window bits 31, best compression). The stream is about 1 MB on the wire.\n* Start a TCP listener on loopback that accepts one connection, reads the request, and answers HTTP/1.1 200 OK with Content-Encoding: gzip, a Content-Length matching the stream, Connection: close, and the stream as body.\n* From a node running a vulnerable hackney, call hackney:request(get, Url, [], <<>>, [{auto_decompress, true}, with_body]) against that listener.\n* Observe the returned body of 1,048,576,000 bytes and the VM memory growing by about 1.8 GB for a 1,019,197 byte response. A larger stream, or an endless body without auto_decompress, drives the node out of memory."}], "x_technicalAnalysis": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p><strong>1. Unbounded accumulation.</strong> <code>hackney:request/5</code> with a body, and <code>hackney:body/1</code> after <code>start_response/1</code>, read the response in <code>src/hackney_conn.erl</code> through <code>read_full_body/2</code>, which appends each chunk to a binary accumulator until the body ends. The HTTP/2 and HTTP/3 synchronous paths accumulate stream data the same way. No option caps the size.</p>\n<p><strong>2. One-step decompression.</strong> With <code>{auto_decompress, true}</code> hackney sends <code>Accept-Encoding: gzip, deflate</code>. Once the body is complete, <code>maybe_decompress_body/2</code> dispatches on <code>Content-Encoding</code> to <code>decompress_gzip/1</code> (<code>zlib:gunzip/1</code>) or <code>decompress_deflate/1</code> (<code>zlib:inflate/2</code>). Both return the whole output at once, so the inflated size is bounded only by the compression ratio. The report measured a 1 MB gzip body inflating to 1 GB on hackney 4.8.4.</p>"}, {"base64": false, "type": "text/markdown", "value": "**1. Unbounded accumulation.** `hackney:request/5` with a body, and `hackney:body/1` after `start_response/1`, read the response in `src/hackney_conn.erl` through `read_full_body/2`, which appends each chunk to a binary accumulator until the body ends. The HTTP/2 and HTTP/3 synchronous paths accumulate stream data the same way. No option caps the size.\n\n**2. One-step decompression.** With `{auto_decompress, true}` hackney sends `Accept-Encoding: gzip, deflate`. Once the body is complete, `maybe_decompress_body/2` dispatches on `Content-Encoding` to `decompress_gzip/1` (`zlib:gunzip/1`) or `decompress_deflate/1` (`zlib:inflate/2`). Both return the whole output at once, so the inflated size is bounded only by the compression ratio. The report measured a 1 MB gzip body inflating to 1 GB on hackney 4.8.4."}], "value": "1. Unbounded accumulation. hackney:request/5 with a body, and hackney:body/1 after start_response/1, read the response in src/hackney_conn.erl through read_full_body/2, which appends each chunk to a binary accumulator until the body ends. The HTTP/2 and HTTP/3 synchronous paths accumulate stream data the same way. No option caps the size.\n\n2. One-step decompression. With {auto_decompress, true} hackney sends Accept-Encoding: gzip, deflate. Once the body is complete, maybe_decompress_body/2 dispatches on Content-Encoding to decompress_gzip/1 (zlib:gunzip/1) or decompress_deflate/1 (zlib:inflate/2). Both return the whole output at once, so the inflated size is bounded only by the compression ratio. The report measured a 1 MB gzip body inflating to 1 GB on hackney 4.8.4."}]}}}

{}

{"affected": [{"affectedData": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["hackney_conn", "hackney"], "packageName": "hackney", "packageURL": "pkg:hex/hackney", "product": "hackney", "programFiles": ["src/hackney_conn.erl", "src/hackney.erl"], "programRoutines": [{"name": "hackney_conn:read_full_body/2"}, {"name": "hackney_conn:maybe_decompress_body/2"}, {"name": "hackney_conn:decompress_gzip/1"}, {"name": "hackney_conn:decompress_deflate/1"}, {"name": "hackney:request/5"}, {"name": "hackney:body/1"}], "repo": "https://github.com/benoitc/hackney", "vendor": "benoitc", "versions": [{"lessThan": "4.9.0", "status": "affected", "version": "2.0.0-beta.1", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["hackney_conn", "hackney"], "packageName": "benoitc/hackney", "packageURL": "pkg:github/benoitc/hackney", "product": "hackney", "programFiles": ["src/hackney_conn.erl", "src/hackney.erl"], "programRoutines": [{"name": "hackney_conn:read_full_body/2"}, {"name": "hackney_conn:maybe_decompress_body/2"}, {"name": "hackney_conn:decompress_gzip/1"}, {"name": "hackney_conn:decompress_deflate/1"}, {"name": "hackney:request/5"}, {"name": "hackney:body/1"}], "repo": "https://github.com/benoitc/hackney", "vendor": "benoitc", "versions": [{"lessThan": "493e8bf83a391548e5101792276ab3fc428fa76c", "status": "affected", "version": "dc41b79339ca0c41e16d3f2dd17172bc2de855d6", "versionType": "git"}]}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Allocation of Resources Without Limits or Throttling vulnerability in hackney_conn in benoitc hackney allows a malicious HTTP server to exhaust client memory via an oversized or highly compressed response body. hackney:request/5 and hackney:body/1 return the whole response body, and nothing bounds how much the connection process buffers. Any server the client requests can trigger it.\n\nhackney_conn:read_full_body/2 and the HTTP/2 and HTTP/3 accumulators append every chunk until the body ends. With {auto_decompress, true} the buffered body is then inflated in one step with zlib:gunzip/1 or zlib:inflate/2, which return the whole output at once.\n\nThis issue affects hackney: from 2.0.0-beta.1 before 4.9.0."}], "id": "CVE-2026-97200", "lastModified": "2026-10-26T14:16:42.180", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 8.2, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}]}, "published": "2026-10-26T14:16:42.180", "references": [{"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://cna.erlef.org/cves/CVE-2026-97200.html"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/benoitc/hackney/commit/493e8bf83a391548e5101792276ab3fc428fa76c"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/benoitc/hackney/commit/dc41b79339ca0c41e16d3f2dd17172bc2de855d6"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/benoitc/hackney/pull/980"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/benoitc/hackney/releases/tag/4.9.0"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://osv.dev/vulnerability/EEF-CVE-2026-97200"}], "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-409"}, {"lang": "en", "value": "CWE-770"}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}]}

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