{"id":"CVE-2026-48095","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-48095","summary":"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…","details":"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.","published":"2026-06-05T15:16:53.520","modified":"2026-06-17T10:54:50.997","cvss":{"score":8.8,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},"epss":{"score":0.01116,"percentile":0.63518,"asOf":"2026-08-20"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[],"fix":null,"references":[{"type":"EXPLOIT","url":"https://securitylab.github.com/advisories/GHSL-2026-140_7-Zip/"},{"type":"WEB","url":"https://sourceforge.net/p/sevenzip/discussion/45797/thread/555e132ba4"},{"type":"EXPLOIT","url":"https://securitylab.github.com/advisories/GHSL-2026-140_7-Zip/"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-06-17T10:54:50.997"}}