CVE-2023-54030: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54030 is a vulnerability in the Linux kernel's io_uring subsystem related to improper handling of multishot receive (recv) Completion Queue Entries (CQEs). The flaw allows multishot recv CQEs to overflow without bound, which can degrade performance and, in the worst case, cause an Out-of-Memory (OOM) condition for the affected task. It affects Linux kernel versions starting from the introduction of the vulnerable code (around commit b3fdea6ecb55) up to the fixes applied in the 6.5.3 and 6.6 stable series. The CVE was published on December 24, 2025, and NVD has not yet assigned a CVSS score; Feedly estimates the severity as Medium (Feedly).

The root cause is insufficient bounds checking in the io_uring/net code path responsible for handling multishot receive operations. When a multishot recv operation is active, the kernel can generate an unbounded number of CQEs without enforcing a limit, leading to uncontrolled memory growth (related to CWE-400: Uncontrolled Resource Consumption). The fix, applied in two stable kernel commits, introduces logic to prevent CQE overflow in the multishot recv path, capping the number of completions to avoid runaway resource usage. Patches are referenced at kernel.org commits 1e2db9837be7 (6.6 stable) and b2e74db55dd9 (6.5.3 stable) (kernel.org patch 1, kernel.org patch 2).

Successful exploitation of this vulnerability can cause significant availability impact on affected Linux systems. An attacker or a misbehaving application leveraging io_uring multishot recv operations could trigger an OOM condition, potentially crashing or severely degrading the performance of the affected task or the entire system. There is no evidence of confidentiality or integrity impact; the primary risk is a denial-of-service condition affecting system stability (Feedly).

The vulnerability is fixed in Linux kernel stable versions 6.5.3 and 6.6 via commits 1e2db9837be7d24a2a74eb3f3906d0872bee8907 and b2e74db55dd93d6db22a813c9a775b5dbf87c560 respectively. Users should update to a patched kernel version (6.5.3+, 6.6+, or a downstream distribution kernel that includes these fixes). SUSE has issued advisories (SUSE-2026-0281-1 and SUSE-2026-20876-1) incorporating these fixes for their kernel packages. As a workaround, restricting unprivileged access to io_uring (e.g., via sysctl kernel.io_uring_disabled=1 or seccomp policies) can reduce exposure until patching is feasible (kernel.org patch 1, kernel.org patch 2, Linux Security SUSE).