Skip to main content
VulnerabilityPublished

CVE-2026-48104: mcmilk 7-Zip · Use of Uninitialized Resource

Affects mcmilk 7-ZipSource CVE Database V5

0
Compare

Not known to be exploited · CVSS 4.2 Medium : upgrade to 26.01 when convenient.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
4.2Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 26.01
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 5 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade mcmilk 7-Zip to 26.01.

Affected software

ProductAffectedFixed in
mcmilk7-ZipAffected
  • >=9.18 <26.01
Fixed in
  • 26.01

AI-suggested

Version 26.01 of 7-Zip fixes this vulnerability. Users should upgrade to 7-Zip 26.01 or later to remediate this issue. Since this is not a cloud service, remediation depends on user action to update the software. Patch status is not explicitly confirmed in the vendor advisory, but the description states the issue is fixed in version 26.01.

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.

References

Community reviews

Loading reviews…