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              "content": {
                "id": "CVE-2026-72854",
                "options": [
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            "tags": [
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            "url": "https://github.com/msgpack/msgpack-c/issues/1181"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "msgpack-c",
          "repo": "https://github.com/msgpack/msgpack-c",
          "vendor": "msgpack",
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              "version": "0",
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      "credits": [
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          "type": "reporter",
          "value": "mtholmquist"
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      ],
      "datePublic": "2026-08-13T00:00:00.000Z",
      "descriptions": [
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          "lang": "en",
          "value": "msgpack_unpacker_expand_buffer in src/unpack.c, reached through the public msgpack_unpacker_reserve_buffer API, computes its new buffer size using an unchecked size_t addition of the requested size and the amount already used. The doubling loop guards its own multiplication against overflow, but the addition in the loop condition is unguarded, so a request near SIZE_MAX wraps: the loop condition is already satisfied, the allocation is performed at the small pre-wrap size, and the function returns true. The caller is told the requested capacity was reserved when it was not, so a subsequent write of the requested length overflows the heap buffer. The library\u0027s own example/lib_buffer_unpack.c demonstrates the reserve-then-write pattern, and its defensive assert comparing capacity against the request is compiled out under NDEBUG. msgpack-c\u0027s own decode entry points do not derive the reservation size from untrusted input, so reaching this requires an integration that passes an attacker-influenced length to the reservation API, such as a length-prefixed streaming transport."
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            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L",
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            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "PASSIVE",
            "vectorString": "CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0",
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            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "HIGH"
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          "descriptions": [
            {
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              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-787",
              "description": "Out-of-bounds Write",
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          "tags": [
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          "tags": [
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          "url": "https://github.com/msgpack/msgpack-c/blob/c-7.0.1/example/lib_buffer_unpack.c"
        },
        {
          "tags": [
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          "url": "https://github.com/msgpack/msgpack-c"
        },
        {
          "name": "VulnCheck Advisory: msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/msgpack-c-integer-overflow-in-msgpack-unpacker-expand-buffer-causes-a-false-success-undersized-reservation"
        }
      ],
      "title": "msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation",
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    "cveId": "CVE-2026-72854",
    "datePublished": "2026-08-20T18:19:24.266Z",
    "dateReserved": "2026-08-10T15:16:31.371Z",
    "dateUpdated": "2026-08-20T18:53:26.891Z",
    "state": "PUBLISHED"
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