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

> An attacker can craft a tar archive to desync the parser, causing content smuggling and incorrect file extraction in async-tar.

- **Severity:** Medium 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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Sep 2026
- **Updated:** 2 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-53600, GHSA-35rm-7j9c-2f7m, UBUNTU-CVE-2026-53600

## What is CVE-2026-53600?

CVE-2026-53600 is a medium-severity vulnerability in dignifiedquire async-tar, published on 2 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-843 (Access of Resource Using Incompatible Type), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-53600?

2 open source packages ship an affected version, including async-tar.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `async-tar` | crates.io | All versions | 0.6.1 |
| `async-tar` | crates.io | All versions | 0.6.1 |

## How do I fix CVE-2026-53600?

Upgrade async-tar to 0.6.1 or later.

## Is CVE-2026-53600 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53600 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53600 and fix it if it is affected.

What it is: CVE-2026-53600 is a medium-severity vulnerability in dignifiedquire async-tar, published on 2 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53600 exists.

Affected packages and fixed versions:
- async-tar (crates.io): affected all versions; fixed in 0.6.1
- async-tar (crates.io): affected all versions; fixed in 0.6.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53600/ (Markdown: https://insights.sbomify.com/CVE-2026-53600/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53600
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53600
- OSV: https://osv.dev/vulnerability/CVE-2026-53600

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53600/
Summaries are generated and may contain mistakes; the official description above is the record.