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What is the vulnerability, what is the attack vector, and how does it work? The technical context from the linked source Edera

This vulnerability is a desynchronization flaw that allows an attacker to "smuggle" additional archive entries into TAR extractions. It occurs when processing nested TAR files that exhibit a specific mismatch between their PAX extended headers and ustar headers.

The flaw stems from the parser's inconsistent logic when determining file data boundaries:

1. A file entry has both PAX and ustar headers.
2. The PAX header correctly specifies the actual file size (size=X, e.g., 1MB).
3. The ustar header incorrectly specifies zero size (size=0).
4. The vulnerable tokio-tar parser incorrectly advances the stream position based on the ustar size (0 bytes) instead of the PAX size (X bytes).

By advancing 0 bytes, the parser fails to skip over the actual file data (which is a nested TAR archive) and immediately encounters the next valid TAR header located at the start of the nested archive. It then incorrectly interprets the inner archive's headers as legitimate entries belonging to the outer archive.

This leads to:

• File overwriting attacks within extraction directories.
• Supply chain attacks via build system and package manager exploitation.
• Bill-of-materials (BOM) bypass for security scanning.