CVE-2020-9369: 
NixOS vulnerability analysis and mitigation

CVE-2020-9369 affects Sympa versions 6.2.38 through 6.2.52. This vulnerability was discovered in February 2020 and allows remote attackers to cause a denial of service through disk consumption from temporary files and flooding notifications to listmasters via malformed parameters (NVD, Sympa Security).

The vulnerability exists in the CSRF prevention mechanism of Sympa's web interface. When processing requests with malformed parameters, particularly those tampering with CSRF tokens, the system creates junk files in Sympa's temporary directory and generates excessive notification messages to listmasters. The vulnerability has been assigned a CVSS v3.1 base score of 7.5 (HIGH) with vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (NVD).

The primary impact of this vulnerability is the potential for denial of service (DoS) through two vectors: disk space exhaustion due to accumulation of junk files in the temporary directory, and system resource consumption from flooding notification messages to listmasters (Sympa Security).

The vulnerability was fixed in Sympa version 6.2.54. For systems unable to upgrade immediately, a patch (sympa-6.2.52-sa-2020-001.patch) was released. The patch should be applied to the wwsympa.fcgi file, followed by a restart of the web interface. No other workarounds were known at the time of disclosure (Sympa Security).

The vulnerability was initially reported by Javier Moreno and tracked through GitHub issue #886. Multiple Linux distributions, including Debian and Fedora, released security updates to address this vulnerability (Debian Security).