async-tar PAX extension-header desync enables tar entry/content smuggling (CVE-2026-53600) | HOL Guard CVE

Medium · CVSS 6.3CVE-2026-53600GHSA-35RM-7J9C-2F7M

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

Answer in brief

CVE-2026-53600 records a Medium severity (CVSS 6.3) vulnerability in async-tar PAX extension-header desync enables tar entry/content smuggling. The current sources do not mark it as known exploited. The current feed maps dignifiedquire/async-tar (generic), async-tar (rust). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 2, 2026Updated Sep 9, 2026Source checked Sep 17, 2026First seen by HOL Jul 8, 2026Material review Sep 9, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.3
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 6.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps dignifiedquire/async-tar (generic), async-tar (rust). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
dignifiedquire/async-targeneric	< 0.6.1	Not reported
async-tarrust	<0.6.1	0.6.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for dignifiedquire/async-tar, async-tar.
Review the reported fix. Update async-tar to 0.6.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 2, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jul 8, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.