CVE-2020-18395: 
NixOS vulnerability analysis and mitigation

CVE-2020-18395 is a NULL-pointer dereference vulnerability discovered in GNU_gama::set() function within ellipsoid.h in Gama 2.04. The vulnerability was disclosed in April 2019 and officially assigned a CVE ID in August 2020 (GNU Mailing List).

The vulnerability exists in the GNU_gama::set() function located in ellipsoid.h file of Gama 2.04. When processing crafted inputs, the function can trigger a NULL-pointer dereference, leading to a segmentation fault. The vulnerability has been assigned a CVSS v3.1 base score of 7.5 HIGH (Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is classified as CWE-476 (NULL Pointer Dereference) (NVD).

The vulnerability can lead to a denial of service (DoS) condition through segment faults when processing specially crafted inputs. The impact is limited to service availability, with no direct impact on confidentiality or integrity (NVD).

The vulnerability can be triggered using specially crafted inputs to the gama-g3 application with the command './gama-g3 --algorithm envelope $POC ./tmp'. Address Sanitizer (ASAN) has confirmed the presence of the vulnerability through segmentation fault detection (GNU Mailing List).

The vulnerability has been fixed in versions after Gama 2.04. Users are advised to upgrade to the latest version of the software (GNU Mailing List).