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CVE-2026-48104— GHSL-2026-120: 7-Zip SquashFS BlockToNode uninitialized heap read

Quick assessment

Affected
mcmilk 7-Zip
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

7-Zip是7-Zip开源的一个压缩软件。 7-Zip 9.18版本至26.00版本存在安全漏洞，该漏洞源于SquashFS存档处理器中索引数组稀疏填充导致未初始化堆读取，可能导致拒绝服务和堆信息泄露。

CVSS 4.2 · Medium EPSS 0.25% · P14

Possible ATT&CK Techniques 2 AI

T1407 T1083 · File and Directory Discovery

Affected Version Matrix 1

VendorProduct Version RangeStatus
mcmilk 7-Zip >= 9.18, < 26.01 affected
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I. Basic Information for CVE-2026-48104

Vulnerability Information
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Vulnerability Title
GHSL-2026-120: 7-Zip SquashFS BlockToNode uninitialized heap read
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
对未经初始化资源的使用
Source: CVE Program / CVE List V5
Vulnerability Title
7-Zip 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
7-Zip是7-Zip开源的一个压缩软件。 7-Zip 9.18版本至26.00版本存在安全漏洞，该漏洞源于SquashFS存档处理器中索引数组稀疏填充导致未初始化堆读取，可能导致拒绝服务和堆信息泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mcmilk 7-Zip >= 9.18, < 26.01 -

II. Public POCs for CVE-2026-48104

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III. Intelligence Information for CVE-2026-48104

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Same Patch Batch · mcmilk · 2026-06-05 · 8 CVEs total

CVE-2026-48095 8.8 HIGH GHSL-2026-140_7-Zip: 7-Zip has a heap buffer overflow via NTFS compressed stream buffer un
CVE-2026-48112 6.5 MEDIUM GHSL-2026-122 7-Zip Ar SYMDEF OOB Read
CVE-2026-48101 6.5 MEDIUM GHSL-2026-117: 7-Zip UEFI Capsule uninitialized heap memory disclosure
CVE-2026-48092 4.3 MEDIUM 7-Zip SquashFS Fragment Offset Overflow (GHSL-2026-116)
CVE-2026-48111 4.3 MEDIUM GHSL-2026-121 7-Zip UEFI DEPEX OOB Read
CVE-2026-48103 4.3 MEDIUM GHSL-2026-119 7-Zip WIM SecurityId OOB read
CVE-2026-48102 3.1 LOW GHSL-2026-118: 7-Zip UDF Field OOB Read

IV. Related Vulnerabilities

Same product: 7-Zip
Same vendor: mcmilk
Same weakness: CWE-908

V. Comments for CVE-2026-48104

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