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CVE-2026-72854

5.3 Moyenne

Publiée le 20/08/2026 à 21:17 · Modifiée le 18/10/2026 à 22:10 · Analyse NVD reportée · Source : disclosure@vulncheck.com

Description

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.

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Produits concernés

Scores CVSS

VersionScoreSourceVecteur
4.0 5.8 Moyenne disclosure@vulncheck.com 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
3.1 5.3 Moyenne disclosure@vulncheck.com (NVD) CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L

Faiblesses (CWE)

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