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.
CVSS Score
4.2
EPSS Score
0.0
Published
2026-06-05
7-Zip is a file archiver with a high compression ratio. Versions 9.11 through 26.00 contain a heap out-of-bounds read of up to 3 bytes in the UDF disc image handler's File Identifier Descriptor parser. In CFileId::Parse (CPP/7zip/Archive/Udf/UdfIn.cpp), after validating size < 38 + idLen + impLen and advancing processed to 38 + impLen + idLen, the alignment-padding loop reads p[processed] while incrementing up to 3 times to reach a 4-byte boundary, and the processed <= size bounds check only runs after the loop. When (38 + impLen + idLen) % 4 != 0 and 38 + impLen + idLen == size, the loop reads 1 to 3 bytes past the end of the exact-size heap buffer allocated via buf.Alloc((size_t)item.Size). The UDF handler is registered for .iso and .udf files and auto-detected by signature, and the OOB read triggers during Open() when listing or extracting a crafted UDF image. Impact is limited to information disclosure (a 1-bit oracle per OOB byte via open/fail behavior) and denial of service (crash under hardened allocators); there is no write primitive. Version 26.01 fixes the issue.
CVSS Score
3.1
EPSS Score
0.0
Published
2026-06-05
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.
CVSS Score
8.8
EPSS Score
0.0
Published
2026-06-05
7-Zip before 25.01 does not always properly handle symbolic links during extraction.
CVSS Score
3.6
EPSS Score
0.002
Published
2025-08-08
7-Zip is a file archiver with a high compression ratio. Zeroes written outside heap buffer in RAR5 handler may lead to memory corruption and denial of service in versions of 7-Zip prior to 25.0.0. Version 25.0.0 contains a fix for the issue.
CVSS Score
5.5
EPSS Score
0.005
Published
2025-07-17
7-Zip is a file archiver with a high compression ratio. 7-Zip supports extracting from Compound Documents. Prior to version 25.0.0, a null pointer dereference in the Compound handler may lead to denial of service. Version 25.0.0 contains a fix cor the issue.
CVSS Score
5.5
EPSS Score
0.004
Published
2025-07-17
CVE-2025-0411
7-Zip Mark-of-the-Web Bypass Vulnerability. This vulnerability allows remote attackers to bypass the Mark-of-the-Web protection mechanism on affected installations of 7-Zip. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within the handling of archived files. When extracting files from a crafted archive that bears the Mark-of-the-Web, 7-Zip does not propagate the Mark-of-the-Web to the extracted files. An attacker can leverage this vulnerability to execute arbitrary code in the context of the current user. Was ZDI-CAN-25456.
Known exploited
CVSS Score
7.0
EPSS Score
0.467
Published
2025-01-25
7-Zip Zstandard Decompression Integer Underflow Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of 7-Zip. Interaction with this library is required to exploit this vulnerability but attack vectors may vary depending on the implementation.
The specific flaw exists within the implementation of Zstandard decompression. The issue results from the lack of proper validation of user-supplied data, which can result in an integer underflow before writing to memory. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-24346.
CVSS Score
7.8
EPSS Score
0.442
Published
2024-11-22
Ppmd7.c in 7-Zip before 23.00 allows an integer underflow and invalid read operation via a crafted 7Z archive.
CVSS Score
7.8
EPSS Score
0.547
Published
2023-11-03
7-Zip through 21.07 on Windows allows privilege escalation and command execution when a file with the .7z extension is dragged to the Help>Contents area. This is caused by misconfiguration of 7z.dll and a heap overflow. The command runs in a child process under the 7zFM.exe process. NOTE: multiple third parties have reported that no privilege escalation can occur
CVSS Score
7.8
EPSS Score
0.189
Published
2022-04-15
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