{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-74755", "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09", "state": "PUBLISHED", "assignerShortName": "apache", "dateReserved": "2026-08-15T06:31:05.828Z", "datePublished": "2026-10-21T11:45:25.658Z", "dateUpdated": "2026-10-21T11:45:25.658Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09", "shortName": "apache", "dateUpdated": "2026-10-21T11:45:25.658Z"}, "title": "Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to Denial of Service", "problemTypes": [{"descriptions": [{"description": "CWE-191 Integer Underflow (Wrap or Wraparound)", "lang": "en", "cweId": "CWE-191", "type": "CWE"}]}], "source": {"discovery": "EXTERNAL"}, "affected": [{"vendor": "Apache Software Foundation", "product": "Apache bRPC", "packageURL": "pkg:github/apache/brpc", "versions": [{"status": "affected", "version": "0", "lessThan": "1.18.0", "versionType": "semver"}], "defaultStatus": "unaffected", "collectionURL": "https://github.com", "packageName": "apache/brpc"}], "descriptions": [{"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\u00a0 https://github.com/apache/brpc/pull/3450", "lang": "en", "supportingMedia": [{"type": "text/html", "base64": false, "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;"}]}], "references": [{"url": "https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb", "tags": ["vendor-advisory"]}], "metrics": [{"other": {"type": "Textual description of severity", "content": {"text": "moderate"}}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "credits": [{"lang": "en", "value": "Feng Zhijie (Independent security researcher)", "type": "finder"}], "x_generator": {"engine": "Vulnogram 0.2.0"}}}}

{}

{"affected": [{"affectedData": [{"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"}]}], "source": "security@apache.org"}], "cveTags": [], "descriptions": [{"lang": "en", "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\u00a0 https://github.com/apache/brpc/pull/3450"}], "id": "CVE-2026-74755", "lastModified": "2026-10-21T12:17:22.550", "metrics": {}, "published": "2026-10-21T12:17:22.550", "references": [{"source": "security@apache.org", "url": "https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb"}], "sourceIdentifier": "security@apache.org", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-191"}], "source": "security@apache.org", "type": "Primary"}]}

{}

{"created": "2026-10-21T18:45:07.107560+00:00", "updated": "2026-10-21T18:45:07.107565+00:00", "vendors": []}