{"id":"CVE-2026-59980","summary":"hpack: Unbounded variable integer decoding can cause run-away computation on malformed input","details":"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.","aliases":["GHSA-8v8h-hg4w-mvq2"],"modified":"2026-09-25T03:48:32.850438075Z","published":"2026-09-23T22:07:35.095Z","related":["openSUSE-SU-2026:11556-1"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59980.json"},"references":[{"type":"WEB","url":"https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a"},{"type":"WEB","url":"https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59980.json"},{"type":"ADVISORY","url":"https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59980"},{"type":"FIX","url":"https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/python-hyper/hpack","events":[{"introduced":"0"},{"fixed":"8cfb02c547740e16dbfe7aba77bad84b297cec2c"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"4.2.0"}]}}],"versions":["v4.1.0","v4.0.0","v3.0.0","v2.3.0","v2.2.0","v2.1.1","v2.1.0","v2.0.1","v2.0.0","v1.1.0","v1.0.1","v1.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-59980.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}