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    "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"
    },
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                "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"
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            ],
            "descriptions": [
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                    "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",
                    "lang": "en",
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                            "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;"
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            "references": [
                {
                    "url": "https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb",
                    "tags": [
                        "vendor-advisory"
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                    "other": {
                        "type": "Textual description of severity",
                        "content": {
                            "text": "moderate"
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                            "value": "GENERAL"
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            "credits": [
                {
                    "lang": "en",
                    "value": "Feng Zhijie (Independent security researcher)",
                    "type": "finder"
                }
            ],
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