{"api_version":"1","generated_at":"2026-10-27T07:13:45+00:00","cve":"CVE-2026-74755","urls":{"html":"https://cve.report/CVE-2026-74755","api":"https://cve.report/api/cve/CVE-2026-74755.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-74755","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-74755"},"summary":{"title":"Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to Denial of Service","description":"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","state":"PUBLISHED","assigner":"apache","published_at":"2026-10-21 12:17:22","updated_at":"2026-10-26 21:10:00"},"problem_types":["CWE-191","CWE-191 CWE-191 Integer Underflow (Wrap or Wraparound)"],"metrics":[],"references":[{"url":"https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb","name":"https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb","refsource":"security@apache.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-74755","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74755","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Apache Software Foundation","product":"Apache bRPC","version":"affected 1.18.0 semver","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"Feng Zhijie (Independent security researcher)","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"74755","cve":"CVE-2026-74755","epss":"0.002020000","percentile":"0.100180000","score_date":"2026-10-26","updated_at":"2026-10-27 00:12:16"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"collectionURL":"https://github.com","defaultStatus":"unaffected","packageName":"apache/brpc","packageURL":"pkg:github/apache/brpc","product":"Apache bRPC","vendor":"Apache Software Foundation","versions":[{"lessThan":"1.18.0","status":"affected","version":"0","versionType":"semver"}]}],"credits":[{"lang":"en","type":"finder","value":"Feng Zhijie (Independent security researcher)"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"An integer underflow in the mcpack2pb component of Apache bRPC (version &lt; 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).<br><br>Root Cause:<br>In 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.<br><br>Affected Scenarios:<br>bRPC 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.<br><br>How to Fix:<br>1. Upgrade bRPC to a version that includes this fix.<br>2. Apply the patch in PR&nbsp;<a target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/apache/brpc/pull/3450\">https://github.com/apache/brpc/pull/3450</a>&nbsp;"}],"value":"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"}],"metrics":[{"other":{"content":{"text":"moderate"},"type":"Textual description of severity"},"scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-191","description":"CWE-191 Integer Underflow (Wrap or Wraparound)","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-10-21T11:45:25.658Z","orgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","shortName":"apache"},"references":[{"tags":["vendor-advisory"],"url":"https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb"}],"source":{"discovery":"EXTERNAL"},"title":"Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to Denial of Service","x_generator":{"engine":"Vulnogram 0.2.0"}}},"cveMetadata":{"assignerOrgId":"f0158376-9dc2-43b6-827c-5f631a4d8d09","assignerShortName":"apache","cveId":"CVE-2026-74755","datePublished":"2026-10-21T11:45:25.658Z","dateReserved":"2026-08-15T06:31:05.828Z","dateUpdated":"2026-10-21T11:45:25.658Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-21 12:17:22","lastModifiedDate":"2026-10-26 21:10:00","problem_types":["CWE-191","CWE-191 CWE-191 Integer Underflow (Wrap or Wraparound)"],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"74755","Ordinal":"1","Title":"Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to De","CVE":"CVE-2026-74755","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"74755","Ordinal":"1","NoteData":"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","Type":"Description","Title":"Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to De"}]}}}