GHSA-3pv8-6f4r-ffg2: Tar Tar Has A PAX Header Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3pv8-6f4r-ffg2",
  "modified" : "2026-05-29T19:16:12Z",
  "published" : "2026-05-29T19:16:12Z",
  "aliases" : [ ],
  "summary" : "tar has a PAX header desynchronization issue",
  "details" : "### Summary\n\nWhen 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`.\n\n[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.\n\nAs 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.\n\n### PoC\n\n[This tar](https://github.com/user-attachments/files/27141941/pax-overrides-extension-header.tar.zip) (zipped for size) demonstrates the desynchronization: with `tar tvf`:\n\n```\n% tar tvf tests/archives/pax-overrides-extension-header.tar \n----------  0 0      0        2048 Dec 31  1969 longname.txt\n----------  0 0      0           0 Dec 31  1969 file_b\n```\n\nwith `tar-rs`:\n\n```\n---- pax_size_does_not_apply_to_extension_headers stdout ----\n\nthread 'pax_size_does_not_apply_to_extension_headers' (250476889) panicked at tests/all.rs:2121:27:\ncalled `Result::unwrap()` on an `Err` value: Custom { kind: Other, error: \"numeric field was not a number: AAAAAAAA when getting cksum for AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\" }\nnote: run with `RUST_BACKTRACE=1` environment variable to display a backtrace\n```\n\nIn 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.\n\n### Impact\n\nThis 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.",
  "severity" : [ ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tar"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.4.46"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.4.45"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/composefs/tar-rs/security/advisories/GHSA-3pv8-6f4r-ffg2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/composefs/tar-rs/pull/454"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/composefs/tar-rs/commit/bab14dd84b411ac16ecb56d4f2d2f7bfb88a9838"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/composefs/tar-rs"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/composefs/tar-rs/releases/tag/0.4.46"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-843" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-29T19:16:12Z",
    "nvd_published_at" : null
  }
}