{"id":"CVE-2026-59980","state":"PUBLISHED","title":"hpack: Unbounded variable integer decoding can cause run-away computation on malformed input","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.","publishedAt":"2026-09-23T22:07:35.095Z","updatedAt":"2026-09-24T13:25:08.900Z","severity":{"score":6.3,"label":"Medium","version":"4.0","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","source":"GitHub_M"},"assigner":"GitHub_M","products":["python-hyper hpack"],"affected":[{"vendor":"python-hyper","product":"hpack","versions":[{"version":"< 4.2.0","status":"affected"}]}],"references":["https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2","https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c","https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a","https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403"],"weaknesses":["CWE-400"],"ingestedAt":"2026-10-29T20:12:32.778Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/59xxx/CVE-2026-59980.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-59980","state":"PUBLISHED","datePublished":"2026-09-23T22:07:35.095Z","dateUpdated":"2026-09-24T13:25:08.900Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-07-07T19:41:00.004Z"},"containers":{"cna":{"title":"hpack: Unbounded variable integer decoding can cause run-away computation on malformed input","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"python-hyper","product":"hpack","versions":[{"version":"< 4.2.0","status":"affected"}]}],"references":[{"url":"https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2","name":"https://github.com/python-hyper/hpack/security/advisories/GHSA-8v8h-hg4w-mvq2","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c","name":"https://github.com/python-hyper/hpack/commit/8cfb02c547740e16dbfe7aba77bad84b297cec2c","tags":["x_refsource_MISC"]},{"url":"https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a","name":"https://cs.opensource.google/go/x/net/+/master:http2/hpack/hpack.go;l=468;drc=8e2b117aee74f6b86c207a808b0255de45c0a18a","tags":["x_refsource_MISC"]},{"url":"https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403","name":"https://docs.rs/http2/0.5.19/src/http2/hpack/decoder.rs.html#403","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":6.3,"baseSeverity":"MEDIUM","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"CWE-400: Uncontrolled Resource Consumption","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-23T22:07:35.095Z"},"source":{"advisory":"GHSA-8v8h-hg4w-mvq2","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-24T13:24:31.887152Z","id":"CVE-2026-59980","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-24T13:25:08.900Z"}}]}}}