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.
Analysis and contextual insights are available on OpenCVE Cloud.
Vendor 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.
Vendor Workaround
Write the tarball to a file with --output FILE, which verifies the checksums, and read that file instead of standard output.
Tracking
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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 |
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| Weaknesses | CWE-354 | |
| CPEs | cpe:2.3:a:hexpm:hex:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Hexpm
Hexpm hex |
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| References |
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| Metrics |
cvssV4_0
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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
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CWE-354
Improper Validation of Integrity Check Value