CVE-2026-48104: 7-zip Out-of-bounds Read

Vulnerability summary

CVE-2026-48104 is a medium (CVSS 4.2) Out-of-bounds Read vulnerability in 7-zip. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 05-06-2026
   PublishedVulnerability first disclosed.
2. 05-06-2026
   Last modifiedVulnerability information updated.

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.

• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.
• CWE-908Use of Uninitialized ResourceThe product uses or accesses a resource that has not been initialized.