tar has a PAX header desynchronization issue

Exploitation

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

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary When a tar stream contains multiple "header" entries prior to a file entry, tar-rs applies the PAX header (x) to the next entry in the stream, regardless of type. For example, a stream of x - L - file (PAX, GNU longname, file) would result in x's extensions being applied to L rather than to file. Per POSIX pax, this is incorrect: a PAX header always applies to a file entry, not any intermediary entries. See the "pax Header Block" section for the specific prescription there. As a result of this, an attacker can contrive a tar containing a sequence of tar headers such that tar-rs applies the PAX header's size extension to the next header in sequence, effectively desynchronizing the stream and enabling tar-rs specific skippage/extraction of members. In other words, a file can be contrived to extract differently on tar-rs than on other tar parsers. PoC This tar (zipped for size) demonstrates the desynchronization: with tar tvf: with tar-rs: In the above case, the PoC is not…

Published by the source

29 May 2026, 19:16 UTC

Last modified by the source

29 May 2026, 19:16 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-3pv8-6f4r-ffg2

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# Patch Next advisory brief: GHSA-3pv8-6f4r-ffg2

Advisory: tar has a PAX header desynchronization issue
IDs: GHSA-3pv8-6f4r-ffg2
Record: https://patchnext.com/advisories/ghsa-3pv8-6f4r-ffg2 (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: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tar 0.4.46. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io tar: affected <= 0.4.45; fixed in 0.4.46

## 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-3pv8-6f4r-ffg2 (GitHub-reviewed advisory GHSA-3pv8-6f4r-ffg2 lists affected ranges: crates.io tar >=0 <=0.4.45)

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