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Public proof of conceptFix available

CVE-2026-48095

A public proof of concept exists; no exploitation attested.

  • Published2026-06-05
  • Fixed in26.01
  • WeaknessCWE-190 · CWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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 << (BlockSizeLog + CompressionUnit), and a crafted image with ClusterSizeLog >= 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.

Timeline

dates in UTC
  1. 2026-06-0515:16CVE publishedNVD

Versions per branch

NVD
7-zip
BranchAffectedFixed in
26.1< 26.0126.01

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • mcmilk 7-Zip
    Affected
    • = <= 26.00no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-06-05

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • 7zipUbuntu:Pro:24.04:LTSall versions · no fixed version listed
  • 7zipUbuntu:Pro:22.04:LTSall versions · no fixed version listed
  • 7zipUbuntu:26.10all versions · no fixed version listed
  • 7zipUbuntu:26.04:LTSall versions · no fixed version listed
  • 7zipUbuntu:25.10all versions · no fixed version listed
  • 7zipSUSE:Linux Enterprise Server for SAP applications 16.0all versions · fixed in 26.01-160000.1.1
  • 7zipSUSE:Linux Enterprise Server for SAP Applications 15 SP6all versions · fixed in 26.01-150400.9.6.1
  • 7zipSUSE:Linux Enterprise Server for SAP Applications 15 SP5all versions · fixed in 26.01-150400.9.6.1

26 more package ranges on OSV.dev

Vendor advisories

  • CVE-2026-48095 Red Hat Product Security

    7-Zip: 7-Zip: Arbitrary code execution via heap buffer overflow in NTFS handler

Full record on NVD

Fix

  1. Update 7-zip to 26.01

Advisories and patches

Detection

read 2026-11-01 01:02 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionpoc2026-06-08
  • CNACVSS 3.18.8known since 2026-10-23
  • CNAweakness (CWE)CWE-190, CWE-787known since 2026-10-23
  • FIRST EPSSEPSS score1.1 %2026-11-09
  • PoC-in-GitHubproof of concept1known since 2026-11-01
  • OSVaffected packages—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
2026-06-05
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

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 << (BlockSizeLog + CompressionUnit), and a crafted image with ClusterSizeLog >= 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.

Is CVE-2026-48095 actively exploited?

A proof-of-concept exploit exists for CVE-2026-48095, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-48095?

CVE-2026-48095 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

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Sources for this record