# GHSA-3pv8-6f4r-ffg2: tar has a PAX header desynchronization issue

> A logic error in tar-rs allows attackers to desynchronize tar streams, causing incorrect file extraction or crashes when processing malicious archives.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 29 May 2026

## What is GHSA-3pv8-6f4r-ffg2?

GHSA-3pv8-6f4r-ffg2 is a vulnerability in tar, published on 29 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

### Summary

When a tar stream contains multiple "header" entries prior to a file entry, tar-rs applies the PAX header (`x`) to the _next_ entry in the stream, regardless of type. For example, a stream of `x -> L -> file` (PAX, GNU longname, file) would result in `x`'s extensions being applied to `L` rather than to `file`.

[Per POSIX pax](https://pubs.opengroup.org/onlinepubs/9799919799/utilities/pax.html), this is incorrect: a PAX header always applies to a file entry, not any intermediary entries. See the "pax Header Block" section for the specific prescription there.

As a result of this, an attacker can contrive a tar containing a sequence of tar headers such that tar-rs applies the PAX header's `size` extension to the next header in sequence, effectively desynchronizing the stream and enabling tar-rs specific skippage/extraction of members. In other words, a file can be contrived to extract differently on tar-rs than on other tar parsers.

### PoC

[This tar](https://github.com/user-attachments/files/27141941/pax-overrides-extension-header.tar.zip) (zipped for size) demonstrates the desynchronization: with `tar tvf`:

```
% tar tvf tests/archives/pax-overrides-extension-header.tar 
----------  0 0      0        2048 Dec 31  1969 longname.txt
----------  0 0      0           0 Dec 31  1969 file_b
```

with `tar-rs`:

```
---- pax_size_does_not_apply_to_extension_headers stdout ----

thread 'pax_size_does_not_apply_to_extension_headers' (250476889) panicked at tests/all.rs:2121:27:
called `Result::unwrap()` on an `Err` value: Custom { kind: Other, error: "numeric field was not a number: AAAAAAAA when getting cksum for AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

In the above case, the PoC is not weaponized, so it jumps into the middle of an entry and subsequently fails the checksum test rather than silently continuing with attacker-controlled archive state.

### Impact

This is very similar to GHSA-j5gw-2vrg-8fgx and GHSA-fp55-jw48-c537 in impact -- an attacker can use this to extract (or not extract) files from a tar stream depending on the tar parser used, which in turn can be used to obscure the presence of malicious files.

## Which versions are affected by GHSA-3pv8-6f4r-ffg2?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `tar` | crates.io | All versions | 0.4.46 |
| `tar` | crates.io | All versions | 0.4.46 |

## How do I fix GHSA-3pv8-6f4r-ffg2?

Upgrade tar to 0.4.46 or later.

## Is GHSA-3pv8-6f4r-ffg2 being exploited?

There is no known exploitation of GHSA-3pv8-6f4r-ffg2 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-3pv8-6f4r-ffg2 and fix it if it is affected.

What it is: GHSA-3pv8-6f4r-ffg2 is a vulnerability in tar, published on 29 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of GHSA-3pv8-6f4r-ffg2 in the wild and no public exploit code.

Affected packages and fixed versions:
- tar (crates.io): affected all versions; fixed in 0.4.46
- tar (crates.io): affected all versions; fixed in 0.4.46

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/GHSA-3pv8-6f4r-ffg2/ (Markdown: https://insights.sbomify.com/GHSA-3pv8-6f4r-ffg2/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-3pv8-6f4r-ffg2

---
From sbomify Insights: https://insights.sbomify.com/GHSA-3pv8-6f4r-ffg2/
Summaries are generated and may contain mistakes; the official description above is the record.