{"id":"CVE-2026-59993","title":"Picotls has NULL pointer dereference during handshake, when running as a client","summary":"Picotls is a TLS protocol library that allows users select different crypto backends based on their use case. In affected revisions through 44bc503, when picotls is used as a `client-side TLS stack`, a peer can send a `HelloRetryRequest`…","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","cvssSource":"cna","cwe":["CWE-476"],"vendor":"h2o","product":"picotls","affected":["picotls < a06ca417a16f9126808bf5cabe6c5e6e0f16ecae"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-06T18:22:20.935065Z"},"published":"2026-10-30","updated":"2026-11-06","sourceUpdated":"2026-11-06T18:24:13.150Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-59993","references":[{"url":"https://github.com/h2o/picotls/security/advisories/GHSA-2xcv-h2pg-m99c","label":"https://github.com/h2o/picotls/security/advisories/GHSA-2xcv-h2pg-m99c"},{"url":"https://github.com/h2o/picotls/pull/608","label":"https://github.com/h2o/picotls/pull/608"},{"url":"https://github.com/h2o/picotls/commit/a06ca417a16f9126808bf5cabe6c5e6e0f16ecae","label":"https://github.com/h2o/picotls/commit/a06ca417a16f9126808bf5cabe6c5e6e0f16ecae"}],"tags":["cve.org"],"epss":0.00247,"epssPercentile":0.16098,"ingestedAt":"2026-11-05T16:24:31.466Z","slug":"CVE-2026-59993","body":"## Overview\n\nPicotls is a TLS protocol library that allows users select different crypto backends based on their use case. In affected revisions through 44bc503, when picotls is used as a `client-side TLS stack`, a peer can send a `HelloRetryRequest` followed by a `spoofed Hello message` that causes a null-pointer dereference. This can terminate the consuming process, including a process performing other work, resulting in denial of service. This issue is fixed in commit a06ca41.\n\n## Affected\n\n- `picotls < a06ca417a16f9126808bf5cabe6c5e6e0f16ecae`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}