7-Zip UDF File Identifier Descriptor parser heap out-of-bounds read
CVE-2026-48102 is a heap out-of-bounds read in 7-Zip's UDF disc image handler affecting versions 9.11 through 26.00. The flaw is in CFileId::Parse in CPP/7zip/Archive/Udf/UdfIn.cpp while parsing a UDF File Identifier Descriptor. After validating that size is at least 38 + idLen + impLen and advancing processed to 38 + impLen + idLen, the code enters an alignment-padding loop that reads p[processed] while incrementing processed up to three times to align to a 4-byte boundary. The bounds check enforcing processed <= size occurs only after this loop. If (38 + impLen + idLen) % 4 != 0 and 38 + impLen + idLen == size, the parser reads 1 to 3 bytes past the end of the exact-size heap buffer allocated with buf.Alloc((size_t)item.Size). The vulnerable code path is reachable in the UDF handler, which is registered for .iso and .udf files and can also be selected by signature-based auto-detection. The issue can be triggered during Open() when 7-Zip lists or extracts a crafted UDF image. Version 26.01 fixes the issue.
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