{"id":"CVE-2026-93599","state":"PUBLISHED","title":"rustls-webpki before 0.103.13 Panic via empty BIT STRING","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.","publishedAt":"2026-09-18T13:20:10.258Z","updatedAt":"2026-09-18T14:15:25.188Z","severity":{"score":8.7,"label":"High","version":"4.0","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","source":"VulnCheck"},"assigner":"VulnCheck","products":["rustls webpki"],"affected":[{"vendor":"rustls","product":"webpki","packageURL":"pkg:cargo/rustls-webpki","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"0.103.13","versionType":"semver"},{"version":"0.104.0-alpha.1","status":"affected","lessThan":"0.104.0-alpha.7","versionType":"semver"}]}],"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"],"weaknesses":["CWE-191"],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/93xxx/CVE-2026-93599.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-93599","state":"PUBLISHED","datePublished":"2026-09-18T13:20:10.258Z","dateUpdated":"2026-09-18T14:15:25.188Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-09-18T11:00:32.755Z"},"containers":{"cna":{"title":"rustls-webpki before 0.103.13 Panic via empty BIT STRING","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"rustls","product":"webpki","packageURL":"pkg:cargo/rustls-webpki","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"0.103.13","versionType":"semver"},{"version":"0.104.0-alpha.1","status":"affected","lessThan":"0.104.0-alpha.7","versionType":"semver"}]}],"references":[{"url":"https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-82j2-j2ch-gfr8)"},{"url":"https://www.vulncheck.com/advisories/rustls-webpki-before-0.103.13-panic-via-empty-bit-string","name":"VulnCheck Advisory: rustls-webpki before 0.103.13 Panic via empty BIT STRING","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","cvssV4_0":{"version":"4.0","vectorString":"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","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":8.7,"baseSeverity":"HIGH"}},{"format":"CVSS","cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-191","lang":"en","description":"Integer Underflow (Wrap or Wraparound)","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-09-18T13:20:10.258Z"},"datePublic":"2026-04-21T00:00:00.000Z","credits":[{"lang":"en","value":"tynus3","type":"reporter"}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-18T14:04:54.272751Z","id":"CVE-2026-93599","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-18T14:15:25.188Z"}}]}}}