{"cve":"CVE-2026-93599","nvd":{"published":"2026-09-18T14:19:11.410","modified":"2026-09-22T20:25:55.870","status":"Awaiting Analysis","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.","cvss_v4":{"vector":"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","score":8.7},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-191"],"references":["https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8","https://www.vulncheck.com/advisories/rustls-webpki-before-0.103.13-panic-via-empty-bit-string","https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:55:23.253742848+00:00"},"epss":{"cve":"CVE-2026-93599","score":0.00346,"percentile":0.28216,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-82j2-j2ch-gfr8","url":"https://osv.dev/vulnerability/GHSA-82j2-j2ch-gfr8","summary":"rustls-webpki: Denial of service via panic on malformed CRL BIT STRING","modified":"2026-09-19T03:55:33.412079637Z","packages":[{"ecosystem":"crates.io","name":"rustls-webpki","purl":"pkg:cargo/rustls-webpki","ranges":["<0.103.13"],"fixed":["0.103.13"]},{"ecosystem":"crates.io","name":"rustls-webpki","purl":"pkg:cargo/rustls-webpki","ranges":[">=0.104.0-alpha.1 <0.104.0-alpha.7"],"fixed":["0.104.0-alpha.7"]}]},{"id":"RUSTSEC-2026-0104","url":"https://osv.dev/vulnerability/RUSTSEC-2026-0104","summary":"Reachable panic in certificate revocation list parsing","modified":"2026-09-19T08:42:27Z","packages":[{"ecosystem":"crates.io","name":"rustls-webpki","purl":"pkg:cargo/rustls-webpki","ranges":[">=0.0.0-0 <0.103.13",">=0.104.0-alpha.1 <0.104.0-alpha.7"],"fixed":["0.103.13","0.104.0-alpha.7"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}