{"id":"DEBIAN-CVE-2026-93599","details":"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.","modified":"2026-09-23T09:00:22.089516684Z","published":"2026-09-18T14:19:11.410Z","upstream":["CVE-2026-93599"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-93599"}],"affected":[{"package":{"name":"rust-rustls-webpki","ecosystem":"Debian:13","purl":"pkg:deb/debian/rust-rustls-webpki?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.102.8-5","0.103.10+ds-1","0.103.13+ds-1","0.103.15+ds-1","0.103.4-1","0.103.4-2","0.103.5-1","0.103.6-1","0.103.7-1","0.103.9+ds-1","0.103.9+ds-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-93599.json"}},{"package":{"name":"rust-rustls-webpki","ecosystem":"Debian:14","purl":"pkg:deb/debian/rust-rustls-webpki?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.103.13+ds-1"}]}],"versions":["0.102.8-5","0.103.10+ds-1","0.103.4-1","0.103.4-2","0.103.5-1","0.103.6-1","0.103.7-1","0.103.9+ds-1","0.103.9+ds-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-93599.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"}]}