{"id":"GHSA-434x-w66g-qw3r","revision":"7618d33377094dd18083c368555a7ad0","records":[{"revision":"7618d33377094dd18083c368555a7ad0","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-434x-w66g-qw3r","aliases":["CVE-2026-25541","RUSTSEC-2026-0007"],"title":"bytes has integer overflow in BytesMut::reserve","description":"# Details\n\nIn 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.\n\nThis vulnerability is also known as [RUSTSEC-2026-0007](https://rustsec.org/advisories/RUSTSEC-2026-0007.html).","state":0,"publishedAt":"2026-02-03T19:17:46+00:00","modifiedAt":"2026-09-10T03:50:33.9958414+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":[{"system":"CVSS_V4","vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/tokio-rs/bytes/security/advisories/GHSA-434x-w66g-qw3r","https://nvd.nist.gov/vuln/detail/CVE-2026-25541","https://github.com/tokio-rs/bytes/commit/d0293b0e35838123c51ca5dfdf468ecafee4398f","https://github.com/tokio-rs/bytes","https://github.com/tokio-rs/bytes/releases/tag/v1.11.1","https://rustsec.org/advisories/RUSTSEC-2026-0007.html"],"sourceUrl":"https://github.com/advisories/GHSA-434x-w66g-qw3r","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-434x-w66g-qw3r","identifiers":["GHSA-434x-w66g-qw3r","CVE-2026-25541","RUSTSEC-2026-0007"]},"retained":false,"historicalAffected":[]}],"coverage":[]}