CVE-2021-30184: 
Linux Debian vulnerability analysis and mitigation

CVE-2021-30184 affects GNU Chess version 6.2.7, allowing attackers to execute arbitrary code via crafted PGN (Portable Game Notation) data. The vulnerability is related to a buffer overflow in the use of a .tmp.epd temporary file in the cmdpgnload and cmdpgnreplay functions in frontend/cmd.cc. The issue was discovered in April 2021 and has been assigned a CVSS 3.1 base score of 7.8 (High) (NVD).

The vulnerability stems from insufficient validation of PGN file input in the cmdpgnload() and cmdpgnreplay() functions. Specifically, in the loop between lines 482-485 of cmd.cc, a specially crafted epdline could overrun the data buffer since the end of the buffer is not checked. The program continues to copy bytes beyond the buffer limit, eventually overwriting the return address on the stack. The issue can be reproduced by setting a breakpoint on the loadpgnas_epd() function and manipulating the temporary file '.tmp.epd' with a buffer overflow payload (GNU Bug Report).

A successful exploitation of this vulnerability could allow attackers to execute arbitrary code with the privileges of the process or cause a Denial of Service condition. The vulnerability requires user interaction, as an attacker would need to entice a user to open a specially crafted PGN file using GNU Chess (Gentoo Advisory).

The vulnerability has been fixed in GNU Chess version 6.2.8-r1 and later. Users are advised to upgrade to the latest version of the software. For Fedora users, patches were released for versions 32, 33, and 34 (Fedora Update), while Debian users received security updates through DLA-4014-1 (Debian LTS).

The GNU Chess maintainers acknowledged the vulnerability report and confirmed the issue, indicating that similar bugs had been found in the past. They committed to reviewing the provided patch for inclusion in a future release (GNU Response).