CVE-2021-23981: 
NixOS vulnerability analysis and mitigation

CVE-2021-23981 is a high-severity vulnerability discovered in Firefox's WebGL implementation that was disclosed on March 23, 2021. The vulnerability affected Firefox versions prior to 87, Firefox ESR versions before 78.9, and Thunderbird versions before 78.9. This security flaw was discovered by security researchers Abraruddin Khan and Omair (Mozilla Advisory).

The vulnerability occurs when a texture upload of a Pixel Buffer Object could confuse the WebGL code to skip binding the buffer used to unpack it. This results in an out-of-bounds read condition in the ANGLE graphics library's LoadRGB8ToBGR565 function. The issue manifests when processing texture data with specific WebGL operations, potentially leading to memory corruption. The vulnerability has a CVSS 3.1 score of 8.1 (High) (Ubuntu CVE).

The vulnerability could result in memory corruption and potentially lead to an exploitable information leak or application crash. In the context of Thunderbird, while the vulnerability exists, it cannot be exploited through email alone since scripting is disabled when reading mail, but remains a potential risk in browser-like contexts (Mozilla Advisory).

The vulnerability was fixed in Firefox 87, Firefox ESR 78.9, and Thunderbird 78.9. Mozilla implemented a patch that ensures proper binding of buffers during texture uploads. Users are advised to upgrade to these versions or later to mitigate the vulnerability (Mozilla Advisory).