CVE-2026-119602

Description

libmspack through 0.11alpha contains an uninitialized memory disclosure vulnerability in the MS-ZIP decompressor that allows attackers to leak heap data via unchecked back-reference distances. Attackers can supply a crafted MS-ZIP CAB file whose first block begins with a back-reference, causing cabd->extract() to write up to 32 KiB of stale heap memory into extracted output.

References

• https://github.com/kyz/libmspack
• https://github.com/kyz/libmspack/blob/v0.11alpha/libmspack/mspack/mszipd.c#L264-L276
• https://github.com/kyz/libmspack/issues/60
• https://hackmd.io/@haindpwn/libmspack-mszip-uninit-window-info-leak
• https://www.vulncheck.com/advisories/libmspack-through-0-11alpha-uninitialized-memory-disclosure-via-ms-zip-decompressor-window