{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-78227", "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "state": "PUBLISHED", "assignerShortName": "NLnet Labs", "dateReserved": "2026-09-07T14:06:21.963Z", "datePublished": "2026-09-16T08:29:52.342Z", "dateUpdated": "2026-09-16T08:29:52.342Z"}, "containers": {"cna": {"title": "Use-after-free in DoQ stream output buffer on reset re-transmission", "datePublic": "2026-09-16T00:00:00.000Z", "affected": [{"vendor": "NLnet Labs", "product": "Unbound", "versions": [{"version": "1.22.0", "status": "affected", "lessThan": "1.26.1", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "NLnet Labs Unbound 1.22.0 up to and including 1.26.1, has a use-after-free vulnerability when compiled for DNS-over-QUIC support with '--with-libngtcp2'. Each DoQ stream owns an output buffer that holds the DNS response. ngtcp2's retransmission buffer keeps a shallow pointer into the output buffer for as long as a STREAM frame may be resent. On a client RESET_STREAM, the output buffer is freed but ngtcp2 still holds the matching retransmission entries. The next PTO timeout makes ngtcp2 re-encode the STREAM frame and copy from the freed buffer. A malicious actor that can query Unbound over DoQ and that withholds ACKs, sends RESET_STREAM, and waits for PTO, reaches this use-after-free with no privilege. This leads to retransmissions against freed memory and eventually an abnormal server exit under a 20-query spray."}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "compiled with DNS-over-QUIC support"}], "cvssV3_1": {"version": "3.1", "baseScore": 6.5, "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L"}}], "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-416", "description": "CWE-416: Use After Free", "type": "CWE"}]}], "solutions": [{"lang": "en", "value": "This issue is fixed starting with version 1.26.1"}], "timeline": [{"time": "2026-08-11T00:00:00.000Z", "lang": "en", "value": "Issue reported by Yuqi Qiu"}, {"time": "2026-08-13T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch"}, {"time": "2026-08-14T00:00:00.000Z", "lang": "en", "value": "Yuqi Qiu verifies patch"}, {"time": "2026-09-16T00:00:00.000Z", "lang": "en", "value": "Fixes released with version 1.26.1"}], "credits": [{"lang": "en", "value": "Yuqi Qiu (Nankai University, AOSP Lab)", "type": "finder"}, {"lang": "en", "value": "Xiang Li (Nankai University, AOSP Lab)", "type": "finder"}], "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-78227.txt", "tags": ["vendor-advisory"]}], "providerMetadata": {"orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "shortName": "NLnet Labs", "dateUpdated": "2026-09-16T08:29:52.342Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Unbound", "vendor": "NLnet Labs", "versions": [{"lessThan": "1.26.1", "status": "affected", "version": "1.22.0", "versionType": "semver"}]}], "source": "sep@nlnetlabs.nl"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "NLnet Labs Unbound 1.22.0 up to and including 1.26.1, has a use-after-free vulnerability when compiled for DNS-over-QUIC support with '--with-libngtcp2'. Each DoQ stream owns an output buffer that holds the DNS response. ngtcp2's retransmission buffer keeps a shallow pointer into the output buffer for as long as a STREAM frame may be resent. On a client RESET_STREAM, the output buffer is freed but ngtcp2 still holds the matching retransmission entries. The next PTO timeout makes ngtcp2 re-encode the STREAM frame and copy from the freed buffer. A malicious actor that can query Unbound over DoQ and that withholds ACKs, sends RESET_STREAM, and waits for PTO, reaches this use-after-free with no privilege. This leads to retransmissions against freed memory and eventually an abnormal server exit under a 20-query spray."}], "id": "CVE-2026-78227", "lastModified": "2026-09-16T09:17:05.987", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 4.2, "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}, "published": "2026-09-16T09:17:05.987", "references": [{"source": "sep@nlnetlabs.nl", "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-78227.txt"}], "sourceIdentifier": "sep@nlnetlabs.nl", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}

{}

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