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.
Advisories

No advisories yet.

Fixes

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.

History

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
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-10-12T15:30:14.126Z

Reserved: 2026-10-08T13:45:02.134Z

Link: CVE-2026-105280

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-12T16:17:02.680

Modified: 2026-10-12T16:17:02.680

Link: CVE-2026-105280

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-12T17:00:14Z

Weaknesses