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

• Severity: medium (CVSS 6.3 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-02 · updated 2026-09-09
• Weakness: CWE-20

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.

Affected products

• dignifiedquire async-tar: before 0.6.1

References

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

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