{"id":"CVE-2026-59980","title":"hpack is an HTTP/2 Header Encoding for Python","summary":"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 en…","severity":"medium","cvss":6.3,"cvssVector":"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","cwe":["CWE-400","CWE-770"],"vendor":"python-hyper","product":"hpack","affected":["hpack < 4.2.0"],"published":"2026-09-23","updated":"2026-09-23","sourceUpdated":"2026-09-23T23:17:11.473","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-59980","references":[{"url":"https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a","label":"security-advisories@github.com"},{"url":"https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403","label":"security-advisories@github.com"},{"url":"https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c","label":"security-advisories@github.com"},{"url":"https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2","label":"security-advisories@github.com"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-59980.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-59980"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2539827"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-59980"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59980"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"cvssSource":"cna","ingestedAt":"2026-09-23T22:33:56.547Z","scores":{"cna":6.3,"vendor":7.5},"slug":"CVE-2026-59980","body":"## Overview\n\nhpack 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Migration Toolkit for Containers, Red Hat Ansible Automation Platform 2, Red Hat Hardened Images, Red Hat OpenShift AI (RHOAI), Red Hat OpenStack Platform 17.1, Red Hat OpenStack Platform 18.0 · no fix planned: Migration Toolkit for Containers, Red Hat Ansible Automation Platform 2, Red Hat Hardened Images, Red Hat OpenShift AI (RHOAI), … · updated 2026-09-23 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-59980.json)","depth":"sunlit","depthScore":35,"depthScoreParts":{"impact":34.7,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}