{"id":"CVE-2026-93599","published":"2026-09-18T14:19:11.410","lastModified":"2026-09-22T20:25:55.870","description":"rustls-webpki through 0.103.12 (and 0.104.0-alpha releases before 0.104.0-alpha.7) contains a reachable panic in bit_string_flags() in src/der.rs. The input guard fails to reject a named-bit BIT STRING whose content is exactly [0x00] (zero padding bits and no data bytes), so raw_bits.len() - 1 underflows on the empty slice and the subsequent index operation panics (subtract-with-overflow in debug, index-out-of-bounds in release). The condition is reachable through the public API BorrowedCertRevocationList::from_der() when a CRL contains an issuingDistributionPoint extension with such an onlySomeReasons value. Exploitation requires an application that explicitly opts in to CRL revocation checking by passing RevocationOptions to verify_for_usage() and that parses CRL bytes obtained from a source the attacker can influence; the default rustls configuration, which does not use RevocationOptions, is unaffected. A crafted CRL causes a denial of service via the panic. Fixed in 0.103.13 and 0.104.0-alpha.7.","cvssScore":7.5,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwes":["CWE-191"],"vendors":[],"products":[],"references":[{"url":"https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8","tags":[]},{"url":"https://www.vulncheck.com/advisories/rustls-webpki-before-0.103.13-panic-via-empty-bit-string","tags":[]},{"url":"https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8","tags":[]}],"exploitRefs":[{"url":"https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8","tags":[]},{"url":"https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8","tags":[]}],"hasPoc":true,"ai":null}