{"schema":"threatline.record/2","record":{"id":"CVE-2026-56386","aliases":[],"summary":"Apache bRPC: Integer Underflow and Out-of-Bounds Read in HTTP/2 DATA Frame Parser","details":"Integer underflow and out-of-bounds read in the HTTP/2 server DATA frame parser in Apache bRPC allows an unauthenticated remote attacker to cause denial of service by sending a malformed DATA frame with the PADDED flag set and a zero-length payload.\n\nRoot Cause:\nThe HTTP/2 DATA frame handler computed the fragment size from the attacker-controlled payload length and, when the PADDED flag was present, decremented the fragment size before ensuring that the frame contained the mandatory pad length byte. A zero-length padded DATA frame could therefore underflow the unsigned fragment size and read the pad length byte past the end of the frame buffer.\n\nAffected Scenarios:\nApache bRPC servers that accept HTTP/2 traffic are affected when a remote client can send crafted HTTP/2 frames to the server. HTTP/2 may be reached through cleartext h2c detection on an HTTP port or through TLS ALPN negotiation.\n\nHow to Fix:\n(Choose one of the following options)\n1. Upgrade Apache bRPC to version 1.18.0, which fixes this issue.\n2. Apply this patch:  https://github.com/apache/brpc/pull/3325 \n\nNote:\nThe fix validates that a padded DATA frame has enough payload bytes for the pad length field before decrementing the fragment size or reading the pad length byte. Malformed zero-length padded DATA frames are rejected with HTTP/2 FRAME_SIZE_ERROR.","categories":["Frameworks"],"product":"Apache bRPC","vendor":"Apache Software Foundation","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-56386","source_modified_at":"2026-10-21T13:07:53.942Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Apache bRPC","vendor":"Apache Software Foundation","versions":[{"status":"affected","version":"0","lessThan":"1.18.0","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-56386","source_modified_at":"2026-10-21T13:07:53.942Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Apache bRPC","ecosystem":null},"version":"1.18.0","basis":"first unaffected version stated in the CVE record"}],"cvss":7.5,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00732,"percentile":0.53817,"score_date":"2026-10-23"},"published_at":"2026-10-21T11:37:47.458Z","modified_at":"2026-10-21T13:07:53.942Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-56386","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-21T13:07:53.942Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-56386","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb","tags":["vendor-advisory"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CISA ADP","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"partial","assessed_at":"2026-10-21T13:07:50.344384Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-21T13:07:53.942Z","content_hash":"ce4727b824c6eb1cfca05ac2f57de0f03ac579de66e650e10870c2c8f778fb03"}}