CVE-2026-23423: 
Linux Kernel vulnerability analysis and mitigation

CVE-2026-23423 is a memory leak vulnerability in the Linux kernel's btrfs file system implementation, specifically within the btrfs_uring_read_extent() function. The pages object allocated during asynchronous I/O read operations is not properly freed in error paths — when allocations fail or btrfs_encoded_read_regular_fill_pages() does not return -EIOCBQUEUED, the cleanup section exits without releasing the pages allocation. Affected kernel versions include 6.13.x through before 6.18.17, 6.19.x before 6.19.7, and 7.0-rc1 through rc7. It was disclosed on April 3, 2026, and carries a CVSS v3.1 base score of 5.5 (Medium) (Red Hat Advisory, Github Advisory).

The root cause is classified as CWE-401 (Missing Release of Memory after Effective Lifetime) and CWE-772 (Missing Release of Resource after Effective Lifetime). In btrfs_uring_read_extent(), the pages object is allocated and expected to be freed by the deferred handler btrfs_uring_read_finished() under normal execution. However, when error conditions occur — such as failed prior allocations or a non--EIOCBQUEUED return from btrfs_encoded_read_regular_fill_pages() — the function falls through to a synchronous cleanup path that frees other resources but omits the pages allocation, resulting in a memory leak. Exploitation requires local access with low privileges and no user interaction (Red Hat Bugzilla, Github Advisory).

Successful exploitation allows a local, low-privileged attacker to trigger memory leaks in the kernel's btrfs I/O subsystem by repeatedly inducing error conditions during btrfs read operations. Over time, accumulated unreleased memory can exhaust available system memory, leading to denial of service through system crashes, hangs, or severe performance degradation. There is no confidentiality or integrity impact; the vulnerability is limited to availability. Only systems using the btrfs file system are affected (Red Hat Advisory, Github Advisory).

Patches are available in Linux kernel versions 6.18.17, 6.19.7, and 7.0-rc3 or later, with fixes committed to stable kernel branches at three separate commits (kernel patch 1, kernel patch 2, kernel patch 3). Administrators should update to a patched kernel version as the primary remediation. For systems that cannot be updated immediately, monitoring btrfs I/O error rates and limiting btrfs-intensive workloads may reduce exposure; systems not using btrfs are unaffected (Red Hat Advisory).