Hex compares a fetched tarball's inner and outer checksums with the repository's signed registry before writing it to a file or unpacking it. The standard output branch of mix hex.package fetch writes the bytes returned by Hex.SCM.fetch/3 without that comparison, and Hex.SCM.fetch/3 doesn't verify freshly downloaded tarballs itself. When a mirror configured with HEX_MIRROR_URL or mirror_url serves altered bytes, the command prints them and exits successfully, while the same fetch with --output FILE fails with a checksum mismatch.
Hex also prints diagnostics to standard output while the command runs: the body of a failed HTTP response from the update check or a registry fetch, and API warnings from the x-hex-message header. A mirror that answers one of those requests with an error whose body is a tar archive gets that archive written to standard output ahead of the verified tarball, so a pipeline that unpacks standard output extracts the mirror's files. This happens even when the checksum check then fails, because the archive is already on standard output.
This issue affects hex: from 0.20.2 before 2.5.2.
No advisories yet.
Solution
Upgrade Hex to 2.5.2 or later, for example with mix local.hex. mix hex.package fetch PACKAGE VERSION --output - then verifies the registry checksum before writing the tarball to standard output and prints its messages to standard error.
Workaround
Write the tarball to a file with --output FILE, which verifies the checksums, and read that file instead of standard output.
Mon, 12 Oct 2026 15:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Improper Validation of Integrity Check Value vulnerability in hexpm hex allows a package mirror to substitute the tarball that mix hex.package fetch PACKAGE VERSION --output - writes to standard output. Hex compares a fetched tarball's inner and outer checksums with the repository's signed registry before writing it to a file or unpacking it. The standard output branch of mix hex.package fetch writes the bytes returned by Hex.SCM.fetch/3 without that comparison, and Hex.SCM.fetch/3 doesn't verify freshly downloaded tarballs itself. When a mirror configured with HEX_MIRROR_URL or mirror_url serves altered bytes, the command prints them and exits successfully, while the same fetch with --output FILE fails with a checksum mismatch. Hex also prints diagnostics to standard output while the command runs: the body of a failed HTTP response from the update check or a registry fetch, and API warnings from the x-hex-message header. A mirror that answers one of those requests with an error whose body is a tar archive gets that archive written to standard output ahead of the verified tarball, so a pipeline that unpacks standard output extracts the mirror's files. This happens even when the checksum check then fails, because the archive is already on standard output. This issue affects hex: from 0.20.2 before 2.5.2. | |
| Title | Hex writes unverified package tarballs to standard output in mix hex.package fetch | |
| First Time appeared |
Hexpm
Hexpm hex |
|
| Weaknesses | CWE-354 | |
| CPEs | cpe:2.3:a:hexpm:hex:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Hexpm
Hexpm hex |
|
| References |
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|
| Metrics |
cvssV4_0
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Projects
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Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-10-12T15:30:14.126Z
Reserved: 2026-10-08T13:45:02.134Z
Link: CVE-2026-105280
No data.
Status : Received
Published: 2026-10-12T16:17:02.680
Modified: 2026-10-12T16:17:02.680
Link: CVE-2026-105280
No data.
OpenCVE Enrichment
Updated: 2026-10-12T16:30:14Z