GHSL-2026-140_7-Zip: 7-Zip has a heap buffer overflow via NTFS compressed stream buffer under-allocation_CVE-2026-48095

{
    "lastseen": "",
    "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.",
    "published": "2026-06-05T13:57:43.772Z",
    "modified": "2026-06-05T13:57:43.772Z",
    "type": "cve",
    "title": "GHSL-2026-140_7-Zip: 7-Zip has a heap buffer overflow via NTFS compressed stream buffer under-allocation",
    "source": "GitHub_M",
    "references": "https://securitylab.github.com/advisories/GHSL-2026-140_7-Zip/\nhttps://sourceforge.net/p/sevenzip/discussion/45797/thread/555e132ba4",
    "id": "CVE-2026-48095",
    "bulletinFamily": "",
    "cwe": [
        "CWE-787",
        "CWE-190"
    ],
    "cvelist": null,
    "sourceData": "mcmilk 7-Zip <= 26.00",
    "sourceHref": "",
    "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",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "7-Zip",
    "version": "<= 26.00",
    "vendor": "Igor Pavlov",
    "ai_description": "Heap buffer overflow via NTFS compressed stream buffer under-allocation in 7-Zip versions 26.00 and prior, potentially allowing arbitrary code execution or application crashes",
    "ai_severity": "High",
    "ai_vendor": "Igor Pavlov",
    "ai_product": "7-Zip",
    "ai_version": "26.00 and prior",
    "ai_score": 8.8
}