{"id":"RUSTSEC-2026-0007","revision":"b6c44e7847034b2ba16815614f3c7547","records":[{"revision":"b6c44e7847034b2ba16815614f3c7547","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"RUSTSEC-2026-0007","aliases":["CVE-2026-25541","GHSA-434x-w66g-qw3r"],"title":"Integer overflow in `BytesMut::reserve`","description":"In the unique reclaim path of `BytesMut::reserve`, the condition\n```rs\nif v_capacity >= new_cap + offset\n```\nuses an unchecked addition. When `new_cap + offset` overflows `usize` in release builds, this condition may incorrectly pass, causing `self.cap` to be set to a value that exceeds the actual allocated capacity. Subsequent APIs such as `spare_capacity_mut()` then trust this corrupted `cap` value and may create out-of-bounds slices, leading to UB.\n\nThis behavior is observable in release builds (integer overflow wraps), whereas debug builds panic due to overflow checks.\n\n## PoC\n\n```rs\nuse bytes::*;\n\nfn main() {\n    let mut a = BytesMut::from(&b\"hello world\"[..]);\n    let mut b = a.split_off(5);\n\n    // Ensure b becomes the unique owner of the backing storage\n    drop(a);\n\n    // Trigger overflow in new_cap + offset inside reserve\n    b.reserve(usize::MAX - 6);\n\n    // This call relies on the corrupted cap and may cause UB & HBO\n    b.put_u8(b'h');\n}\n```\n\n# Workarounds\n\nUsers of `BytesMut::reserve` are only affected if integer overflow checks are configured to wrap. When integer overflow is configured to panic, this issue does not apply.","state":0,"publishedAt":"2026-02-03T12:00:00+00:00","modifiedAt":"2026-10-12T18:00:09.239419+00:00","affected":[{"ecosystem":"crates.io","name":"bytes","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"1.2.1"},{"kind":"fixed","version":"1.11.1"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://crates.io/crates/bytes","https://rustsec.org/advisories/RUSTSEC-2026-0007.html","https://github.com/tokio-rs/bytes/commit/d0293b0e35838123c51ca5dfdf468ecafee4398f"],"sourceUrl":"https://osv.dev/vulnerability/RUSTSEC-2026-0007","license":"OSV · upstream source license applies","key":"osv:RUSTSEC-2026-0007","identifiers":["RUSTSEC-2026-0007","CVE-2026-25541","GHSA-434x-w66g-qw3r"]},"retained":false,"historicalAffected":[]}],"coverage":[]}