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CVE-2026-48101 mcmilk CVE debrief

CVE-2026-48101 is a MEDIUM severity vulnerability in 7-Zip, a file archiver with a high compression ratio. Versions 9.21 through 26.00 are affected by an uninitialized memory disclosure vulnerability in the UEFI capsule (.scap) parser. The OpenCapsule function allocates a heap buffer of attacker-declared CapsuleImageSize (up to 1 GiB) without zero-initialization, then reads the file contents into it. If the file is truncated, the unread tail of the buffer retains uninitialized heap memory, which is then exposed as extracted file content via GetStream. Version 26.0.1 fixes the issue.

Vendor
mcmilk
Product
7-Zip
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-05
Original CVE updated
2026-06-11
Advisory published
2026-06-05
Advisory updated
2026-06-11

Who should care

Users of 7-Zip versions 9.21 through 26.00 should update to version 26.0.1 or later to mitigate this vulnerability.

Technical summary

The vulnerability exists in the UEFI capsule (.scap) parser of 7-Zip. The OpenCapsule function allocates a heap buffer without zero-initialization, leading to potential exposure of uninitialized memory if the file is truncated.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update 7-Zip to version 26.0.1 or later.

Evidence notes

CVE-2026-48101 has a CVSS score of 6.5 and is classified as MEDIUM severity. The vulnerability was published on 2026-06-05T16:16:41.423Z and modified on 2026-06-11T18:02:03.633Z.

Official resources

CVE-2026-48101 was published on 2026-06-05T16:16:41.423Z and modified on 2026-06-11T18:02:03.633Z.