Out-of-bounds Read Affecting 7zip package, versions <26.01-r0


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.18% (8th percentile)

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  • Snyk IDSNYK-ALPINE324-7ZIP-17376617
  • published19 Jun 2026
  • disclosed5 Jun 2026

Introduced: 5 Jun 2026

CVE-2026-48104  (opens in a new tab)
CWE-125  (opens in a new tab)
CWE-908  (opens in a new tab)

How to fix?

Upgrade Alpine:3.24 7zip to version 26.01-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream 7zip package and not the 7zip package as distributed by Alpine. See How to fix? for Alpine:3.24 relevant fixed versions and status.

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 Base Scores

version 3.1