High
7zip, p7zip — security advisory
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.
- Products
- 7zip, p7zip
- Affected versions
- 16.02+dfsg-4, 16.02+dfsg-5, 16.02+dfsg-6, 16.02+dfsg-7, 16.02+dfsg-7build1, 16.02+dfsg-8, 21.03~beta+dfsg-6, 21.04~beta+dfsg-1, 21.06+dfsg-1, 21.07+dfsg-1, 21.07+dfsg-2, 21.07+dfsg-3, 21.07+dfsg-4, 21.07+dfsg-4ubuntu0.1~esm1, 23.01+dfsg-11, 23.01+dfsg-11ubuntu0.1~esm1, 23.01+dfsg-3, 23.01+dfsg-7, 23.01+dfsg-8, 24.09+dfsg-7, 24.09+dfsg-8, 25.00+dfsg-1, 25.01+dfsg-1, 25.01+dfsg-2, 25.01+dfsg-3, 25.01+dfsg-4, 25.01+dfsg-5, 26.00+dfsg-1, 26.01+dfsg-2, 26.01+dfsg-3, 26.02+dfsg-1, 26.02+dfsg-2, 9.20.1~dfsg.1-4, 9.20.1~dfsg.1-4+deb7u1build0.14.04.1, 9.20.1~dfsg.1-4+deb7u2build0.14.04.1, 9.20.1~dfsg.1-4+deb7u3build0.14.04.1, 9.20.1~dfsg.1-4.2, 9.20.1~dfsg.1-4.2ubuntu0.1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-48095
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:07 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-48095
p7zip
Fixed versions: Not specified
p7zip
Fixed versions: Not specified
p7zip
Fixed versions: Not specified
p7zip
Fixed versions: Not specified
p7zip
Fixed versions: Not specified
7zip
Fixed versions: Not specified
7zip
Fixed versions: Not specified
7zip
Fixed versions: Not specified
7zip
Fixed versions: Not specified
7zip
Fixed versions: Not specified
Complete source record
{
"id": "40440b20cfbd0e40c6de5a78508c276e7e968619864be96d9d135ae7abd4cfd1",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-48095",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-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 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.",
"evidence": "osv:UBUNTU-CVE-2026-48095",
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{
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{
"value": "21.06+dfsg-1",
"evidence": "/affected/5/versions"
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{
"value": "21.07+dfsg-1",
"evidence": "/affected/5/versions"
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{
"value": "21.07+dfsg-2",
"evidence": "/affected/5/versions"
},
{
"value": "21.07+dfsg-3",
"evidence": "/affected/5/versions"
},
{
"value": "21.07+dfsg-4",
"evidence": "/affected/5/versions"
},
{
"value": "21.07+dfsg-4ubuntu0.1~esm1",
"evidence": "/affected/5/versions"
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},
{
"name": {
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"evidence": "/affected/6/package/name"
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"affected_versions": [
{
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{
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{
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{
"name": {
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"affected_versions": [
{
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"evidence": "/affected/7/versions"
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{
"value": "24.09+dfsg-8",
"evidence": "/affected/7/versions"
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{
"value": "25.00+dfsg-1",
"evidence": "/affected/7/versions"
},
{
"value": "25.01+dfsg-1",
"evidence": "/affected/7/versions"
},
{
"value": "25.01+dfsg-2",
"evidence": "/affected/7/versions"
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{
"name": {
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"evidence": "/affected/8/package/name"
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{
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"evidence": "/affected/8/versions"
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{
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"evidence": "/affected/8/versions"
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{
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"evidence": "/affected/8/versions"
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{
"value": "26.02+dfsg-1",
"evidence": "/affected/8/versions"
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{
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"evidence": "/affected/9/versions"
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{
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"severity": "high",
"structured": {
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"aliases": [
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"metrics": [
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"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
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},
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"16.02+dfsg-8"
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{
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"ecosystem": "Ubuntu:Pro:22.04:LTS"
},
"versions": [
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"21.06+dfsg-1",
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"21.07+dfsg-3",
"21.07+dfsg-4",
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"ecosystem_specific": {
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},
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},
{
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},
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}
},
{
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"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
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"25.01+dfsg-3",
"25.01+dfsg-4",
"25.01+dfsg-5",
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],
"database_specific": {
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},
"ecosystem_specific": {
"binaries": [
{
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},
{
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}
]
}
}
],
"modified": "2026-10-17T13:00:22.081380991Z",
"provider": "osv",
"upstream": [
"CVE-2026-48095"
],
"references": [
"https://ubuntu.com/security/CVE-2026-48095",
"https://www.cve.org/CVERecord?id=CVE-2026-48095",
"https://securitylab.github.com/advisories/GHSL-2026-140_7-Zip/"
]
},
"related_cves": [
{
"value": "CVE-2026-48095",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 360442,
"published_at": "2026-06-05T15:16:00+00:00"
}