PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. In versions 4.0.0 through 5.8.0, 3.3.0 through 3.10.6, 2.2.0 through 2.4.6, 2.0.0 through 2.1.17, and all releases up to and including 1.30.5, the Gnumeric reader reads attacker-supplied .gnumeric files into memory and, when the file starts with gzip magic bytes, calls gzdecode() on the full compressed contents without enforcing a decompressed-size limit. A very small compressed .gnumeric file can expand to data larger than the PHP memory limit and crash the process during Gnumeric::canRead() before the file is rejected or fully parsed. This is reachable through normal file-type detection and Gnumeric loading paths, so applications that accept attacker-controlled spreadsheet uploads can suffer denial of service. This issue has been fixed in versions 5.8.1, 3.10.7, 2.4.7, 2.1.18 and 1.30.6.