CVE-2026-48103: 7-Zip heap out-of-bounds read in WIM archive handler

CVE-2026-48103 · Severity: medium · CVSS 4.3 · Published 2026-06-05

7-Zip is a widely used open-source file archiver for compressing and decompressing data. A vulnerability in how it handles Windows Imaging (WIM) files could allow a specially crafted archive to cause the application to crash or disclose small amounts of memory. This occurs automatically when a user simply opens a folder containing the malicious file in the 7-Zip interface, potentially leading to a denial of service or a minor leak of internal program information.

Technologies: 7-Zip. Vendors: 7-Zip.

Quick answers

Is CVE-2026-48103 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-48103 being exploited in the wild.
How severe is CVE-2026-48103?
Medium severity, with a CVSS score of 4.3, published 5 June 2026.
Which products and versions are affected?
7-Zip 9.34 through 26.00.
Is there a fix for CVE-2026-48103?
A patch was published on 2026-04-27: Version 26.01 released with fixes. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-48103 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-48103?
Check whether you run 7-Zip at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An off-by-one heap out-of-bounds read exists in CHandler::GetSecurity within CPP/7zip/Archive/Wim/WimHandler.cpp. The SecurOffsets table holds numEntries + 1 cumulative offsets, but the bounds check (securityId >= SecurOffsets.Size()) incorrectly permits a securityId equal to numEntries. This causes the function to read one UInt32 past the end of the heap-allocated CRecordVector. The securityId is attacker-controlled via WIM metadata. The vulnerability is reachable via the GUI (7zFM.exe) during directory listing or via the CLI. Impact is primarily denial of service (crash) or minor information disclosure; no write primitive is available. Fixed in version 26.01.

Affected products

  • 7-Zip 7-Zip 9.34 through 26.00

Timeline

  • 2026-04-21: disclosed: Reported to vendor via SourceForge private issues.
  • 2026-04-27: patched: Version 26.01 released with fixes.
  • 2026-06-05: advisory: NVD publication date.

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