Vulnerability RUSTSEC-2026-0429

ZipArchive::extract() sizes the symlink-target buffer from the uncompressed size declared in the central directory record, before reading a single byte of entry data:

let mut target = Vec::with_capacity(file.size() as usize);

Both inputs are attacker-controlled. ZipFile::size() returns uncompressed_size verbatim from the central directory, widened to a full u64 by a ZIP64 extended-information extra field, and is never cross-checked against the compressed size, the remaining archive length, or any platform-appropriate bound for a symlink target. ZipFile::is_symlink() is decided entirely by the S_IFLNK bit of the external-attributes field.

Vec::with_capacity() is infallible: when the reservation is refused it calls handle_alloc_error() and aborts the process. This is not a Rust panic. It is not caught by catch_unwind(), is unaffected by panic = "unwind", and is not contained by running the call on a worker thread.

A 112-byte archive is sufficient. One Stored entry flagged S_IFLNK with a ZIP64 field declaring uncompressed_size = 2^62 and a zero-byte payload makes extract() fail with:

memory allocation of 4611686018427387904 bytes failed
Aborted (core dumped)          # exit 134

The declared value only needs to exceed the host's address space, not its RAM: Vec::with_capacity() maps address space without touching pages, so resident memory stays flat and the abort happens on the refused reservation itself. Under a ulimit -v cap or a memory-constrained container the threshold drops far enough that a plain 32-bit uncompressed_size with no ZIP64 field suffices.

Applications that extract archives from untrusted input are affected on Unix and Windows targets with default features and no special configuration: upload handling, mail-attachment processing, package and artefact ingestion, backup restore and container-image layer extraction. No confidentiality or integrity property is affected: there is no memory unsafety, no out-of-bounds access, no disclosure and no data corruption.

The fix landed in zip-rs/zip2#984 and shipped in 9.0.0.

For further details see: https://github.com/zip-rs/zip2/security/advisories/GHSA-q7v9-x93c-xqv3