tar-rs incorrectly ignores PAX size headers if header size is nonzero

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-33055: 0.41% estimated exploitation activity in the next 30 days; percentile 35.55 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary As part of CVE-2025-62518 the astral-tokio-tar project was changed to correctly honor PAX size headers in the case where it was different from the base header. However, it was missed at the time that this project (the original Rust tar crate) had a conditional logic that skipped the PAX size header in the case that the base header size was nonzero - almost the inverse of the astral-tokio-tar issue. The problem here is that any discrepancy in how tar parsers honor file size can be used to create archives that appear differently when unpacked by different archivers. In this case, the tar-rs (Rust tar) crate is an outlier in checking for the header size - other tar parsers (including e.g. Go archive/tar) unconditionally use the PAX size override. Details https://github.com/astral-sh/tokio-tar/blob/aafc2926f2034d6b3ad108e52d4cfc73df5d47a4/src/archive.rs#L578-L600 https://github.com/alexcrichton/tar-rs/blob/88b1e3b0da65b0c5b9750d1a75516145488f4793/src/archive.rs#L339-L344 PoC…

Published by the source

20 Mar 2026, 17:25 UTC

Last modified by the source

19 May 2026, 16:06 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-gchp-q4r4-x4ff

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# Patch Next advisory brief: CVE-2026-33055

Advisory: tar-rs incorrectly ignores PAX size headers if header size is nonzero
IDs: CVE-2026-33055, GHSA-gchp-q4r4-x4ff
Record: https://patchnext.com/advisories/cve-2026-33055 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tar 0.4.45. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io tar: affected <= 0.4.44; fixed in 0.4.45

## Suggested inspection (read-only)
- crates.io tar: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on tar.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-gchp-q4r4-x4ff (GitHub-reviewed advisory GHSA-gchp-q4r4-x4ff lists affected ranges: crates.io tar >=0 <=0.4.44)

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