async-tar PAX extension-header desync enables tar entry/content smuggling

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-53600: 0.45% estimated exploitation activity in the next 30 days; percentile 38.73 (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 async-tar v0.6.0 mis-applies a buffered PAX size extension to an intermediary extension header (a GNU longname L, a GNU longlink K, or a PAX x/g header) instead of to the next file entry. POSIX requires a PAX extended-header record set to describe the next file entry, never an intervening extension header. Because pollnextraw (src/archive.rs) threads the buffered PAX records into the size computation of whatever raw header it reads next — and that header can be an intermediary L — the stream cursor is advanced by an attacker-chosen amount when the L body is consumed. The parser then desyncs relative to a POSIX-correct tar parser (e.g. GNU tar), reading subsequent bytes at the wrong block boundary. An attacker who can influence a tar stream that an async-tar consumer extracts can construct an x → L → file sequence whose entry list and on-disk result differ between async-tar and a reference parser. This enables content/entry smuggling: a file that a GNU-tar-based…

Published by the source

8 Jul 2026, 20:24 UTC

Last modified by the source

8 Jul 2026, 20:24 UTC

Source last checked

26 Oct 2026, 15:43 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-35rm-7j9c-2f7m

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# Patch Next advisory brief: CVE-2026-53600

Advisory: async-tar PAX extension-header desync enables tar entry/content smuggling
IDs: CVE-2026-53600, GHSA-35rm-7j9c-2f7m
Record: https://patchnext.com/advisories/cve-2026-53600 (revision 1, source checked 26 Oct 2026, 15:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: async-tar 0.6.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io async-tar: affected < 0.6.1; fixed in 0.6.1

## Suggested inspection (read-only)
- crates.io async-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 async-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-35rm-7j9c-2f7m (GitHub-reviewed advisory GHSA-35rm-7j9c-2f7m lists affected ranges: crates.io async-tar >=0 <0.6.1)

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