astral-tokio-tar is a tar archive reading/writing library for async Rust. Versions of astral-tokio-tar prior to 0.5.6 contain a boundary parsing vulnerability that allows attackers to smuggle additional archive entries by exploiting inconsistent PAX/ustar header handling. When processing archives with PAX-extended headers containing size overrides, the parser incorrectly advances stream position based on ustar header size (often zero) instead of the PAX-specified size, causing it to interpret file content as legitimate tar headers. This issue has been patched in version 0.5.6. There are no workarounds.
Affected: crates.io: astral-tokio-tar, crates.io: tokio-tar
## Summary
Versions of `astral-tokio-tar` prior to 0.5.6 contain a boundary parsing vulnerability that allows attackers to smuggle additional archive entries by exploiting inconsistent PAX/ustar header handling. When processing archives with PAX-extended headers containing size overrides, the parser incorrectly advances stream position based on ustar header size (often zero) instead of the PAX-specified size, causing it to interpret file content as legitimate tar headers.
This vulnerability was disclosed to multiple Rust tar parsers, all derived from the original `async-tar` fork of `tar-rs`.
## Details
### Vulnerability Description
The vulnerability stems from inconsistent handling of PAX extended headers versus ustar headers when determining file data boundaries. Specifically:
1. **PAX header** correctly specifies the file size (e.g., `size=1048576`) 2. **ustar header** incorrectly specifies zero size (`size=000000000000`) 3. **tokio-tar** advances the stream position based on the ustar size (0 bytes) 4. **Inner content** is then interpreted as legitimate outer archive entries
### Attack Mechanism
When a TAR file contains:
- An outer entry with PAX `size=N` but ustar `size=0` - File data that begins with valid TAR header structures - The parser treats inner content as additional outer entries
This creates a **header/data desynchronization** where the parser's position becomes misaligned with actual file boundaries.
### Root Cause
```rust // Vulnerable: Uses ust…
python311-uv-0.9.5-1.1 on GA media
Affected: crates.io: astral-tokio-tar
Versions of astral-tokio-tar prior to 0.5.6 contain a boundary parsing vulnerability that allows attackers to smuggle additional archive entries by exploiting inconsistent PAX/ustar header handling. When processing archives with PAX-extended headers containing size overrides, the parser incorrectly advances stream position based on ustar header size (often zero) instead of the PAX-specified size, causing it to interpret file content as legitimate tar headers.
This vulnerability was disclosed to multiple Rust tar parsers, all derived from the original async-tar fork of tar-rs.
For additional information see [Edera's blog post](https://edera.dev/stories/tarmageddon).
Security update for python-uv
Affected: Ubuntu:25.10: rust-astral-tokio-tar, Ubuntu:26.04:LTS: rust-astral-tokio-tar
astral-tokio-tar is a tar archive reading/writing library for async Rust. Versions of astral-tokio-tar prior to 0.5.6 contain a boundary parsing vulnerability that allows attackers to smuggle additional archive entries by exploiting inconsistent PAX/ustar header handling. When processing archives with PAX-extended headers containing size overrides, the parser incorrectly advances stream position based on ustar header size (often zero) instead of the PAX-specified size, causing it to interpret file content as legitimate tar headers. This issue has been patched in version 0.5.6. There are no workarounds.