# CVE-2026-48095: 7-Zip heap buffer overflow in NTFS handler

Source: https://junglewise.ai/threats/cve-2026-48095-7-zip-heap-buffer-overflow-in-ntfs-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-05. Updated: 2026-06-05  
License: CC BY 4.0 with a link back

CVE-2026-48095 · Severity: high · CVSS 8.8 · Published 2026-06-05

7-Zip is a widely used file archiving utility. A vulnerability in how it handles NTFS disk images allows an attacker to execute malicious code or crash the application when a user opens or tests a specially crafted file. Because 7-Zip automatically identifies file types by their content, this attack can be triggered even if the malicious file is renamed to look like a standard .zip or .7z archive.

## Quick answers

**Is CVE-2026-48095 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-48095 being exploited in the wild.

**How severe is CVE-2026-48095?** High severity, with a CVSS score of 8.8, published 5 June 2026.

**Which products and versions are affected?** Igor Pavlov 7-Zip 26.00 and prior.

**Is there a fix for CVE-2026-48095?** A patch was published on 2026-04-27: Version 26.01 released with fix. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-48095 attacked?** It is attacked over the network or with local access, in a software library.

**Am I affected by CVE-2026-48095?** Check whether anything you run is named in the advisory. 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

A heap buffer overflow exists in the NTFS archive handler of 7-Zip (7z.dll). The root cause is an undefined behavior (UB) during a 32-bit left-shift operation in CInStream::GetCuSize(), where a crafted NTFS image with specific ClusterSizeLog and CompressionUnit values results in a 1-byte allocation for _inBuf. Subsequent calls to ReadStream_FALSE write up to 256 MB of attacker-controlled data into this 1-byte buffer. This leads to a vtable hijack of the CInStream object, which is located near the buffer on the heap. The vulnerability is reachable regardless of file extension due to 7-Zip's signature-based fallback mechanism. Fixed in version 26.01.

## Affected products

- Igor Pavlov 7-Zip 26.00 and prior

## Timeline

- 2026-04-24: disclosed: Reported to vendor via SourceForge private issue.
- 2026-04-27: patched: Version 26.01 released with fix.
- 2026-06-05: advisory: CVE-2026-48095 published.

## References

- [https://sourceforge.net/p/sevenzip/discussion/45797/thread/555e132ba4](https://sourceforge.net/p/sevenzip/discussion/45797/thread/555e132ba4)