{"id":"GHSA-xr22-8pqp-gwfh","aliases":["RUSTSEC-2026-0337"],"status":"published","title":"Poly1305 panics or computes a wrong tag on attacker-chosen messages of 64 bytes or more","description":"`Poly1305` in `ic-cipher` absorbs messages of 64 bytes or more four blocks at\na time, summing four products before one reduction. From 0.2.5 to 0.2.19 the\nreduction kept its carries in 32-bit integers, which four summed products can\noverflow when the message's bytes are large.\n\nThis affects `Poly1305` and `ChaCha20Poly1305`, and everything built on them:\nthe TLS and QUIC ChaCha20-Poly1305 suites in `ic-rustls`, HPKE with that\ncipher in `ic-hpke`, and the re-exports in `ic-mac` and `ironcrypto`.\n\nWhat happens depends on how the crate was compiled:\n\n- With overflow checks on (any debug build, or a release profile with\n  `overflow-checks = true`) the multiplication panics, and under\n  `panic = \"abort\"` the process ends. The tag is computed over the ciphertext\n  before it is compared, so this happens before authentication and without\n  the key: anyone who can deliver a ChaCha20-Poly1305 ciphertext to be opened\n  can trigger it.\n- With overflow checks off (Cargo's default for release builds) the\n  arithmetic wraps and the tag is computed wrong on the affected messages.\n\nOrdinary data does not reach the defect. A message of `0xff` bytes does: in\none measurement against 0.2.19, 28 of 500 `ChaCha20Poly1305::open_detached`\ncalls on 1,024 bytes of `0xff` under random keys and nonces panicked in a\ndebug build. ChaCha20-Poly1305 derives a new Poly1305 key for every nonce, so\neach message is a fresh attempt.\n\nAES-GCM and AES-GCM-SIV are not affected, and neither are messages shorter\nthan 64 bytes.\n\nThe flaw was corrected in 0.2.20 by carrying in 64 bits.\n\nIt was found by running Project Wycheproof's ChaCha20-Poly1305 test vectors\nagainst the library.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","from":"osv"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"published":"2026-10-09T12:00:00Z","modified":"2026-10-12T18:15:01Z","fixes":[{"ecosystem":"crates.io","package":"ic-cipher","fixed_in":["0.2.20"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"crates.io","package":"ic-cipher","ranges":[{"type":"SEMVER","events":[{"introduced":"0.2.5"},{"fixed":"0.2.20"}]}]}],"references":[{"url":"https://crates.io/crates/ic-cipher","tags":["package"]},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0337.html","tags":["advisory"]},{"url":"https://github.com/nervosys/IronCrypto/commit/a8160a18b5c66288f05dc62f5ea2159c687b9416","tags":["web"]}],"sources":{"osv":[{"id":"RUSTSEC-2026-0337","title":"Poly1305 panics or computes a wrong tag on attacker-chosen messages of 64 bytes or more","description":"`Poly1305` in `ic-cipher` absorbs messages of 64 bytes or more four blocks at\na time, summing four products before one reduction. From 0.2.5 to 0.2.19 the\nreduction kept its carries in 32-bit integers, which four summed products can\noverflow when the message's bytes are large.\n\nThis affects `Poly1305` and `ChaCha20Poly1305`, and everything built on them:\nthe TLS and QUIC ChaCha20-Poly1305 suites in `ic-rustls`, HPKE with that\ncipher in `ic-hpke`, and the re-exports in `ic-mac` and `ironcrypto`.\n\nWhat happens depends on how the crate was compiled:\n\n- With overflow checks on (any debug build, or a release profile with\n  `overflow-checks = true`) the multiplication panics, and under\n  `panic = \"abort\"` the process ends. The tag is computed over the ciphertext\n  before it is compared, so this happens before authentication and without\n  the key: anyone who can deliver a ChaCha20-Poly1305 ciphertext to be opened\n  can trigger it.\n- With overflow checks off (Cargo's default for release builds) the\n  arithmetic wraps and the tag is computed wrong on the affected messages.\n\nOrdinary data does not reach the defect. A message of `0xff` bytes does: in\none measurement against 0.2.19, 28 of 500 `ChaCha20Poly1305::open_detached`\ncalls on 1,024 bytes of `0xff` under random keys and nonces panicked in a\ndebug build. ChaCha20-Poly1305 derives a new Poly1305 key for every nonce, so\neach message is a fresh attempt.\n\nAES-GCM and AES-GCM-SIV are not affected, and neither are messages shorter\nthan 64 bytes.\n\nThe flaw was corrected in 0.2.20 by carrying in 64 bits.\n\nIt was found by running Project Wycheproof's ChaCha20-Poly1305 test vectors\nagainst the library.","status":"published","published":"2026-10-09T12:00:00Z","modified":"2026-10-12T18:15:01.974078373Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:53:40.430679Z"}]}}