CVE-2026-105280

6.9Medium

Published 12 Oct 2026 · NVD status: Deferred · AI triage by gemini-3.8-flash

6.9Medium

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Active
Impact: High impact on integrity
Weakness: CWE-354

Impact

A malicious or compromised package mirror can inject arbitrary tarballs or code into build pipelines. They need control over your configured Hex mirror and a workflow that pipes `mix hex.package fetch --output -` directly to an extractor.

Root cause

The stdout output branch of `mix hex.package fetch` streams raw downloaded bytes without running the registry checksum checks that normal file downloads perform.

Affected systems

Hex 0.20.2 before 2.5.2

CVSS v4.0 · 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/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

Fix & remediation

Upgrade Hex to version 2.5.2 or later. If upgrading immediately is not possible, do not pipe standard output using `--output -`; download to a named file using `--output FILE` so Hex validates the checksum.

shell

$ mix local.hex --force

AI-suggested. Run it in staging first and check it against the vendor advisory. Why?

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NVD 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.

References

Source: nvd.nist.gov/vuln/detail/CVE-2026-105280