Upstream information
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.SUSE information
Overall state of this security issue: Pending
This issue is currently rated as having moderate severity.
| CVSS detail | CNA (VulnCheck) | SUSE |
|---|---|---|
| Base Score | 5.3 | 5.3 |
| Vector | CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L | CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:L |
| Attack Vector | Local | Local |
| Attack Complexity | High | High |
| Privileges Required | None | None |
| User Interaction | Required | Required |
| Scope | Unchanged | Unchanged |
| Confidentiality Impact | None | None |
| Integrity Impact | High | High |
| Availability Impact | Low | Low |
| CVSSv3 Version | 3.1 | 3.1 |
| CVSS detail | CNA (VulnCheck) |
|---|---|
| Base Score | 5.8 |
| Vector | 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 |
| Attack Vector | Local |
| Attack Complexity | High |
| Attack Requirements | Present |
| Privileges Required | None |
| User Interaction | Passive |
| Vulnerable System Confidentiality Impact | None |
| Vulnerable System Integrity Impact | High |
| Vulnerable System Availability Impact | Low |
| Subsequent System Confidentiality Impact | None |
| Subsequent System Integrity Impact | None |
| Subsequent System Availability Impact | None |
| CVSSv4 Version | 4.0 |
Status of this issue by product and package
Please note that this evaluation state might be work in progress, incomplete or outdated. Also information for service packs in the LTSS phase is only included for issues meeting the LTSS criteria. If in doubt, feel free to contact us for clarification. The updates are grouped by state of their lifecycle. SUSE product lifecycles are documented on the lifecycle page.
| Product(s) | Source package | State |
|---|---|---|
| Products under general support and receiving all security fixes. | ||
| SUSE Linux Enterprise Server 16.0 | msgpack-c | Affected |
| SUSE Linux Enterprise Server 16.1 | msgpack-c | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | msgpack-c | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | msgpack-c | Affected |
| openSUSE Leap 16.0 | msgpack-c | Affected |
SUSE Timeline for this CVE
CVE page created: Fri Aug 21 12:10:03 2026CVE page last modified: Fri Aug 21 15:47:15 2026