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    2 vulnerabilities found for msgpack-c by msgpack

    CVE-2026-72854 (GCVE-0-2026-72854)

    Vulnerability from nvd – Published: 2026-08-20 18:19 – Updated: 2026-08-20 18:53
    VLAI
    Title
    msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation
    Summary
    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's 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's 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.
    Severity
    5.3 (Medium)
    CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
    5.8 (Medium)
    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
    SSVC
    Exploitation: poc Automatable: no Technical Impact: partial
    CISA Coordinator · CISA-ADP (v2.0.3)
    Decision recorded 2026-08-20 18:52 UTC
    CWE
    • CWE-190 - Integer Overflow or Wraparound
    • CWE-787 - Out-of-bounds Write
    Assigner
    References
    Impacted products
    Vendor Product Version
    msgpack msgpack-c Affected: 0 , ≤ 7.0.1 (custom)
    		Create a notification for this product.
    Date Public
    2026-08-13 00:00
    Credits
    mtholmquist
    Show details on NVD website
    To clipboard 

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    CVE-2026-72854 (GCVE-0-2026-72854)

    Vulnerability from cvelistv5 – Published: 2026-08-20 18:19 – Updated: 2026-08-20 18:53
    VLAI
    Title
    msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation
    Summary
    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's 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's 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.
    Severity
    5.3 (Medium)
    CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L
    5.8 (Medium)
    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
    SSVC
    Exploitation: poc Automatable: no Technical Impact: partial
    CISA Coordinator · CISA-ADP (v2.0.3)
    Decision recorded 2026-08-20 18:52 UTC
    CWE
    • CWE-190 - Integer Overflow or Wraparound
    • CWE-787 - Out-of-bounds Write
    Assigner
    References
    Impacted products
    Vendor Product Version
    msgpack msgpack-c Affected: 0 , ≤ 7.0.1 (custom)
    		Create a notification for this product.
    Date Public
    2026-08-13 00:00
    Credits
    mtholmquist
    Show details on NVD website
    To clipboard 

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