{"schema":"threatline.record/2","record":{"id":"CVE-2026-74755","aliases":[],"summary":"Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to Denial of Service","details":"An integer underflow in the mcpack2pb component of Apache bRPC (version < 1.18.0) on all platforms allows remote attackers to crash a bRPC server by sending a request containing a string field with a zero value_size. The UnparsedValue::as_string() function computes `_size - 1` without validating `_size`; when value_size is 0 the expression underflows to SIZE_MAX, resize() throws std::length_error, and because the exception is not caught on the request parsing path the process aborts (SIGABRT).\n\nRoot Cause:\nIn src/mcpack2pb/parser.cpp, UnparsedValue::as_string() resizes the output string to `_size - 1`, where `_size` is the value_size of a string field taken directly from the network data. A value_size of 0 underflows the unsigned size_t, and the subsequent resize() throws an exception that is not caught.\n\nAffected Scenarios:\nbRPC servers that accept nshead frames wired to the ubrpc mcpack2 adaptor (for example the NsheadService + UbrpcMcpack2Adaptor deployment pattern) can be crashed by a single unauthenticated request. Stock open-source bRPC registers the ubrpc/nshead_mcpack protocols as client-only, so default server configurations are not affected.\n\nHow to Fix:\n1. Upgrade bRPC to a version that includes this fix.\n2. Apply the patch in PR  https://github.com/apache/brpc/pull/3450","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-2026-74755","source_modified_at":"2026-10-21T11:45:25.658Z","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-2026-74755","source_modified_at":"2026-10-21T11:45:25.658Z","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":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00202,"percentile":0.09612,"score_date":"2026-10-23"},"published_at":"2026-10-21T11:45:25.658Z","modified_at":"2026-10-21T11:45:25.658Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-74755","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-21T11:45:25.658Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-74755","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","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-21T11:45:25.658Z","content_hash":"9287fe681f43fd31c9700bcb2d55266e748767ba150313368d296a3fa16895b1"}}