{"id":"CVE-2026-59980","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-59980","generatedAt":"2026-10-28T04:34:50.407Z","title":"As a workaround, sanitize input to hpack decoder for long sequences of `0xFF` values to prevent malicious use.","description":"hpack is an HTTP/2 Header Encoding for Python. Prior to version 4.2.0, unbounded variable integer decoding can cause run-away computation on malformed input leading to O(n^2) runtime, effectively blocking further processing with large enough unsanitized input. A fix is available in python-hyper/hpack v4.2.0 to restricted variable integer decoding to uint32 to prevent run-away computation. As a workaround, sanitize input to hpack decoder for long sequences of `0xFF` values to prevent malicious use.","published":"2026-09-23T23:17:11.000Z","lastModified":"2026-09-30T17:32:07.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"4.0","score":6.3,"severity":"MEDIUM","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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/M"},"cwe":["CWE-400"],"affected":[],"epss":{"score":0.00302,"percentile":0.2275,"date":"2026-10-27","history":[{"date":"2026-09-24","score":0.00301,"percentile":0.20297}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.30%). Track it; it rarely justifies an emergency change on its own."},"changes":[{"kind":"new","label":"New CVE","at":"2026-09-23T23:17:11.000Z","detail":{"score":"6.3","severity":"MEDIUM","publishedAt":"2026-09-23T23:17:11.473Z"},"summary":"New CVE, medium severity (CVSS 6.3)."}],"references":[{"url":"https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a","source":"security-advisories@github.com"},{"url":"https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403","source":"security-advisories@github.com"},{"url":"https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c","source":"security-advisories@github.com"},{"url":"https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-59980","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}