Threat database

7-Zip is a file archiver with a high compression ratio. Versions 9.18 through 26.00 contain a heap out-of-bounds read in 7-Zip Ar handler BSD SYMDEF parser. A 4-byte heap out-of-bounds read exists in the Unix ar archive parser in 7-Zip. When parsing a BSD-style __.SYMDEF symbol table, the ParseLibSymbols function reads a 32-bit namesSize field via Get32 at a position that can equal the buffer size, reading 4 bytes past the end of the heap allocation. This reads uninitialized heap data under the default allocator. Version 26.01 patches the issue.

7-Zip is a file archiver with a high compression ratio. Versions 9.21 through 26.00 contain an off-by-one out-of-bounds read vulnerability in the ParseDepedencyExpression function of the UEFI firmware image parser(CPP/7zip/Archive/UefiHandler.cpp). The function validates an attacker-controlled opcode byte using > instead of >= against the element count of the 10-entry kExpressionCommands static array, allowing an opcode value of 10 to read one pointer slot (8 bytes on x64) past the end of the array in .rodata. The out-of-bounds value is then dereferenced as a const char * and passed through strlen and memcpy into the archive's Characts property, which may cause either a denial of service (access violation when the adjacent bytes do not form a valid readable pointer) or a minor information disclosure of an adjacent .rdata string literal into archive metadata. The vulnerability is reached automatically during IInArchive::Open() via the call path OpenFv/OpenCapsule → ParseVolume → ParseSections when processing a SECTION_DXE_DEPEX (0x13) or SECTION_PEI_DEPEX (0x1B) section whose first body byte is 0x0A, and the UEFI handler is enabled by default in stock 7z.dll with signature-based detection for both UEFIc and UEFIf formats. The outcome (crash vs. silent leak) is deterministic per build but linker-layout dependent, with no write primitive and no disclosure of heap data, secrets, or ASLR base addresses. Version 26.01 fixes the issue.

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.

7-Zip is a file archiver with a high compression ratio. Versions 9.34 through 26.00 contain an off-by-one heap out-of-bounds read in the WIM (Windows Imaging) archive handler's security descriptor lookup. In CHandler::GetSecurity (CPP/7zip/Archive/Wim/WimHandler.cpp), the per-image SecurOffsets table holds numEntries + 1 cumulative offsets, but the check securityId >= SecurOffsets.Size() admits securityId == numEntries, and the function then reads SecurOffsets[securityId + 1], fetching one UInt32 past the end of the heap-allocated CRecordVector (which performs no bounds checking on operator[]). The securityId is attacker-controlled at offset +0xC of any directory entry in WIM metadata, and the handler is registered for .wim, .swm, .esd, and .ppkg and enabled by default in stock 7z.dll; the OOB triggers zero-click in the GUI because 7zFM.exe's ListView calls GetRawProp(kpidNtSecure) for every item during listing (ASan-confirmed), and is also reachable via CLI listing with 7zz l -slt. Impact is limited to denial of service under hardened allocators and minor information disclosure, since the OOB value is only consumed arithmetically as a length and is not surfaced to the attacker; there is no write primitive.

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.

7-Zip is a file archiver with a high compression ratio. Versions 9.21 through 26.00 contain an An uninitialized memory disclosure vulnerability in the UEFI capsule (.scap) parser in 7-Zip. The OpenCapsule function allocates a heap buffer of attacker-declared CapsuleImageSize (up to 1 GiB) without zero-initialization, then reads the file contents into it with ReadStream_FALSE whose return value is silently discarded. If the file is truncated, the unread tail of the buffer retains uninitialized heap memory, which is then exposed as extracted file content via GetStream. Version 26.0.1 fixes the issue.

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.

A heap memory disclosure vulnerability exists in 32-bit builds of 7-Zip versions 9.34 through 26.00 due to an integer overflow in the SquashFS ReadBlock function. This overflow allows an attacker-controlled offset to bypass fragment bounds checks, causing memcpy to read memory preceding the cache buffer into the extracted file. The issue is fixed in version 26.01. The vulnerability has a medium severity rating with a CVSS score of 4.3.