CVE-2026-48104

Description

7-Zip is a file archiver with a high compression ratio. Versions 9.18 through 26.00 contain an uninitialized heap read in the SquashFS archive handler caused by a sparsely populated index array. In the SquashFS handler, _blockToNode is allocated with capacity for every metadata block but populated only when an inode crosses a block boundary, so a crafted image with few inodes spanning many blocks leaves most slots holding raw heap contents (the underlying allocator does not zero-initialize POD storage). When OpenDir looks up an attacker-influenced blockIndex (derived from the RootInode superblock field), it reads two of these uninitialized slots and passes them as the left/right bounds of a binary search over _nodesPos, which dereferences the midpoint without bounds checking; if the resulting value happens to match the search key, the returned index is used to read a full node struct from _nodes whose fields feed further directory parsing, forming a chained OOB read primitive that is heap-layout-dependent and not reliably triggerable. The SquashFS handler is enabled by default in stock 7z.dll and the issue triggers during Open() with no interaction beyond opening the file; impact is denial of service from wild-pointer dereference and potential heap information disclosure, with no write primitive. Version 26.01 fixes the issue.

CVSS 3.1

4.2 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L

EPSS

0.18% probability · 8th percentile

CISA KEV

Not listed

Weakness

CWE-125, CWE-908

Affected

7-zip/7-zip

Source

security-advisories@github.com

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.