7-Zip is a file archiver with a high compression ratio. Versions 9.18 through 26.00 contain an uninitialized heap read in the SquashFS archive handler caused by a sparsely populated index array. In the SquashFS handler, _blockToNode is allocated with capacity for every metadata block but populated only when an inode crosses a block boundary, so a crafted image with few inodes spanning many blocks leaves most slots holding raw heap contents (the underlying allocator does not zero-initialize POD storage). When OpenDir looks up an attacker-influenced blockIndex (derived from the RootInode superblock field), it reads two of these uninitialized slots and passes them as the left/right bounds of a binary search over _nodesPos, which dereferences the midpoint without bounds checking; if the resulting value happens to match the search key, the returned index is used to read a full node struct from _nodes whose fields feed further directory parsing, forming a chained OOB read primitive that is heap-layout-dependent and not reliably triggerable. The SquashFS handler is enabled by default in stock 7z.dll and the issue triggers during Open() with no interaction beyond opening the file; impact is denial of service from wild-pointer dereference and potential heap information disclosure, with no write primitive. Version 26.01 fixes the issue.
PUBLISHED5.2CWE-908CWE-125
GHSL-2026-120: 7-Zip SquashFS BlockToNode uninitialized heap read
Problem type
Affected products
mcmilk
7-Zip
>= 9.18, < 26.01 - AFFECTED
References
JSON source
https://cveawg.mitre.org/api/cve/CVE-2026-48104Click to expand
{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-48104",
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"dateUpdated": "2026-06-05T15:56:34.744Z",
"dateReserved": "2026-05-20T18:40:45.836Z",
"datePublished": "2026-06-05T15:56:34.744Z",
"state": "PUBLISHED"
},
"containers": {
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"shortName": "GitHub_M",
"dateUpdated": "2026-06-05T15:56:34.744Z"
},
"title": "GHSL-2026-120: 7-Zip SquashFS BlockToNode uninitialized heap read",
"descriptions": [
{
"lang": "en",
"value": "7-Zip is a file archiver with a high compression ratio. Versions 9.18 through 26.00 contain an uninitialized heap read in the SquashFS archive handler caused by a sparsely populated index array. In the SquashFS handler, _blockToNode is allocated with capacity for every metadata block but populated only when an inode crosses a block boundary, so a crafted image with few inodes spanning many blocks leaves most slots holding raw heap contents (the underlying allocator does not zero-initialize POD storage). When OpenDir looks up an attacker-influenced blockIndex (derived from the RootInode superblock field), it reads two of these uninitialized slots and passes them as the left/right bounds of a binary search over _nodesPos, which dereferences the midpoint without bounds checking; if the resulting value happens to match the search key, the returned index is used to read a full node struct from _nodes whose fields feed further directory parsing, forming a chained OOB read primitive that is heap-layout-dependent and not reliably triggerable. The SquashFS handler is enabled by default in stock 7z.dll and the issue triggers during Open() with no interaction beyond opening the file; impact is denial of service from wild-pointer dereference and potential heap information disclosure, with no write primitive. Version 26.01 fixes the issue."
}
],
"affected": [
{
"vendor": "mcmilk",
"product": "7-Zip",
"versions": [
{
"version": ">= 9.18, < 26.01",
"status": "affected"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"description": "CWE-908: Use of Uninitialized Resource",
"cweId": "CWE-908",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"lang": "en",
"description": "CWE-125: Out-of-bounds Read",
"cweId": "CWE-125",
"type": "CWE"
}
]
}
],
"references": [
{
"url": "https://securitylab.github.com/advisories/GHSL-2026-115_GHSL-2026-122_7-zip/",
"name": "https://securitylab.github.com/advisories/GHSL-2026-115_GHSL-2026-122_7-zip/",
"tags": [
"x_refsource_CONFIRM"
]
}
],
"metrics": [
{
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L",
"attackVector": "NETWORK",
"attackComplexity": "HIGH",
"privilegesRequired": "NONE",
"userInteraction": "REQUIRED",
"scope": "UNCHANGED",
"confidentialityImpact": "LOW",
"integrityImpact": "NONE",
"availabilityImpact": "LOW",
"baseScore": 4.2,
"baseSeverity": "MEDIUM"
}
}
]
}
}
}