CVE-2026-72854
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
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.
Risk Assessment
This can lead to a heap buffer overflow, potentially enabling remote code execution or application crash if an integration passes an attacker-controlled length to the reservation API.
Recommendation
Upgrade msgpack-c to a patched version. Ensure integrations do not pass attacker-controlled lengths to the reservation API without validation.
Related vulnerabilities
- CVE-2026-119506Critical
The Frontend Admin by DynamiApps plugin (acf-frontend-form-element) through version 3.30.1 contains an incorrect privilege assignment vulnerability. The flaw allows an attacker to escalate privileges within the WordPress site.
- CVE-2026-6715Critical
IBM Concert 1.0 through 3.0.1.1 allows an attacker to supply crafted input that is incorporated into an operating system command without adequate validation or sanitization. Successful exploitation allows remote attackers to execute arbitrary commands on the underlying operating system with the privileges of the affected service.
- CVE-2026-17466Critical
IBM Optim versions 1.0.0, 1.1.0, and 1.2.0 are vulnerable to path traversal, allowing a remote authenticated attacker to obtain sensitive information.
- CVE-2026-15266Critical
IBM Concert 1.0 through 3.0.1.1 contains components that allow potentially unsafe command execution, which could be exploited to run arbitrary system commands on the host.
- CVE-2026-114464Critical
IBM Process Mining 2.0.0 through 2.2.1 has improper access control, which could allow a remote attacker to obtain sensitive information.
- CVE-2026-107331Critical
IBM DataStage on Cloud Pak for Data 5.4.0.0 has an absolute-path traversal vulnerability that could allow a remote authenticated attacker to obtain sensitive information.
- CVE-2026-109900Critical
The Melapress Role Editor plugin for WordPress (through version 1.3.0) contains an incorrect privilege assignment vulnerability that allows privilege escalation. A low-privileged user can gain a higher level of access within the system.
- CVE-2026-101117Critical
IBM WebSphere Extreme Scale versions 8.6.1.0 through 8.6.2.2 have an improper Content Security Policy configuration that could allow a remote attacker to bypass security restrictions. The flaw concerns browser-side protection mechanisms.
- CVE-2026-124494Critical
SunEditor before 3.4.0 contains a stored cross-site scripting vulnerability because the html.clean() sanitizer's _normalizeURL() function decodes named entities like : to an empty string. Attackers can inject href values such as javascript: that pass the _isSafeURL() check but are decoded by browsers, executing JavaScript when victims click stored links.
- CVE-2026-124493Critical
SunEditor before 3.4.0 contains a stored cross-site scripting vulnerability in the DocumentType constructor that injects header textContent into innerHTML without HTML escaping. Attackers can store entity-encoded HTML in h1-h6 headers that executes JavaScript when editors using document:header mode initialize, enabling session cookie theft.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS