Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
mcmilk 7-Zip — GHSL-2026-140_7-Zip: 7-Zip has a heap buffer overflow via NTFS compressed stream buffer under-allocation
AV AC PR UI S C I A CVSS EPSS %ile KEV
N L N R U H H H 8.8 .0112 63.5 —
AFFECTED
Product Versions Fixed
7-Zip <= 26.00 – —
TIMELINE
May 20 Reserved by GitHub_M
Jun 5 EXPLOIT PUBLISHED — CVE-2026-48095 (mcmilk 7-Zip). Public exploit reference added.
Jun 5 Published (CNA: GitHub_M)
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.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
|---|
| May 20, 2026 | Reserved | Reserved by GitHub_M |
| June 5, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-48095 (mcmilk 7-Zip). Public exploit reference added. |
| June 5, 2026 | Published | Published (CNA: GitHub_M) |
Affected
Affected products and packages — 1 row
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| mcmilk | 7-Zip | — | <= 26.00 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-48095 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.