CVE-2021-4009: 
Rocky Linux vulnerability analysis and mitigation

A flaw was found in xorg-x11-server in versions before 21.1.2 and before 1.20.14. An out-of-bounds access vulnerability was discovered in the SProcXFixesCreatePointerBarrier function. The vulnerability was identified and reported by Jan-Niklas Sohn working with Trend Micro Zero Day Initiative (X.Org Advisory, ZDI Advisory).

The vulnerability exists within the handling of SProcXFixesCreatePointerBarrier requests in the XFixes extension. The issue stems from improper validation of request length, which can lead to out-of-bounds memory write. The vulnerability has been assigned a CVSS v3.1 base score of 7.8 (HIGH) with the vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD, NetApp Advisory).

The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability. Successful exploitation could lead to local privilege escalation on systems where the X server is running privileged and remote code execution for ssh X forwarding sessions (X.Org Advisory, ZDI Advisory).

The vulnerability requires local access and low privileges to exploit. An attacker must first obtain the ability to execute low-privileged code on the target system. The attacker can then leverage this vulnerability to escalate privileges and execute arbitrary code in the context of root (ZDI Advisory).

The vulnerability has been fixed in xorg-server versions 21.1.2 and 1.20.14. Users are advised to upgrade to these or later versions. The fix was implemented through a patch (commit b5196750099ae6ae582e1f46bd0a6dad29550e02) that addresses the out-of-bounds access in the XFixes extension (X.Org Advisory, Debian Advisory).

Multiple Linux distributions and vendors have released security advisories and patches for this vulnerability, including Debian, Fedora, Ubuntu, and NetApp. The vulnerability was initially discovered and reported through the Zero Day Initiative program, highlighting the importance of coordinated vulnerability disclosure (Debian Advisory, NetApp Advisory).