# CVE-2026-105280: Hex writes unverified package tarballs to standard output in mix hex.package fetch

> A malicious mirror can inject unverified tarballs into stdout during package fetch, potentially leading to code execution or data modification in pipelines.

- **Severity:** Medium 6.9 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 12 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-105280, EEF-CVE-2026-105280, GHSA-98jr-23pm-vj7c, UBUNTU-CVE-2026-105280

## What is CVE-2026-105280?

CVE-2026-105280 is a medium-severity vulnerability in hexpm hex, published on 12 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-354 (Improper Validation of Integrity Check Value)

## Which versions are affected by CVE-2026-105280?


## How do I fix CVE-2026-105280?

Upgrade to a fixed version.

## Is CVE-2026-105280 being exploited?

There is no known exploitation of CVE-2026-105280 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-105280 and fix it if it is affected.

What it is: CVE-2026-105280 is a medium-severity vulnerability in hexpm hex, published on 12 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-105280 in the wild and no public exploit code.

Affected product: hexpm hex. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-105280/ (Markdown: https://insights.sbomify.com/CVE-2026-105280/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-105280
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-105280
- OSV: https://osv.dev/vulnerability/CVE-2026-105280

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-105280/
Summaries are generated and may contain mistakes; the official description above is the record.