# CVE-2026-48095 — mcmilk 7-Zip

> As of 2026-06-08, CVE-2026-48095 is a HIGH-severity vulnerability in mcmilk 7-Zip, CVSS v3.1 8.8, EPSS 0.0% (19.2th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-48095, most recently “7-Zip NTFS Handler Heap Overflow CVE-2026-48095 — vtable Hijack via Crafted Archive (GHSL-2026-140)”.

**Last updated:** 2026-06-08

## What is CVE-2026-48095?

7-Zip is a file archiver with a high compression ratio. Versions 26.00 and prior contain a heap buffer overflow vulnerability caused by an under-allocation in the NTFS compressed stream buffer (GetCuSize shift UB), potentially allowing attackers to cause arbitrary code execution or application crashes. CInStream::GetCuSize() in the NTFS handler computes the compression-unit buffer size as (UInt32)1 = 28 and CompressionUnit == 4 drives the exponent to 32, which is undefined behavior and collapses on x86/x64 so _inBuf is allocated as 1 byte. ReadStream_FALSE then writes up to 256 MB of attacker-controlled data into that 1-byte buffer in 64 KB iterations, and because the CInStream object sits only 304 bytes after _inBuf, its vtable pointer is overwritten and the next dispatched call achieves a vtable hijack. On 32-bit builds the overflow is unconditionally reached; on 64-bit it requires the parallel 8 GB _outBuf allocation to succeed, otherwise failing closed to denial of service. The NTFS handler is enabled by default in stock 7z.dll and, via signature-based fallback matching "NTFS " at offset 3, will open a crafted image regardless of file extension during extraction or testing. Version 26.01 fixes the issue.

The record classifies CVE-2026-48095 under weakness classes [CWE-787](https://cwe.mitre.org/data/definitions/787.html), [CWE-190](https://cwe.mitre.org/data/definitions/190.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 108 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 8.8 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **EPSS (FIRST):** 0.0% probability of exploitation in the next 30 days, higher than 19.2% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-06-05, last modified 2026-06-08

## Is CVE-2026-48095 being exploited?

It currently carries a trending score of 13 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **mcmilk**: 7-Zip

## How to fix CVE-2026-48095

No vendor patch reference has been recorded for CVE-2026-48095 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-48095

1 tracked threat in the Threadlinqs corpus references CVE-2026-48095, either in the campaign’s CVE list or as an indicator on the campaign record.

- [7-Zip NTFS Handler Heap Overflow CVE-2026-48095 — vtable Hijack via Crafted Archive (GHSL-2026-140)](https://intel.threadlinqs.com/threat/TL-2026-0586) — HIGH · 2026-05-26

## Sources

Seeded from `cveorg` and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

- [securitylab.github.com](https://securitylab.github.com/advisories/GHSL-2026-140_7-Zip/)
- [sourceforge.net](https://sourceforge.net/p/sevenzip/discussion/45797/thread/555e132ba4)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-48095
Full detection coverage and IOCs for threats exploiting CVE-2026-48095 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp