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PatchSiren cyber security CVE debrief

CVE-2026-45995 Linux CVE debrief

A use-after-free (UAF) vulnerability in the Linux kernel's io_uring subsystem, specifically within the zero-copy receive (zcrx) ring buffer handling. The flaw occurs in `io_free_rbuf_ring()` which accesses a `struct user_struct` that `io_zcrx_ifq_free()` has already put (decremented reference count), leading to potential memory corruption or privilege escalation. The vulnerability was resolved by ensuring proper reference counting order during ring destruction.

Vendor
Linux
Product
Unknown
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-05-27
Advisory published
2026-05-27
Advisory updated
2026-05-27

Who should care

Linux system administrators, kernel maintainers, and security teams operating systems with io_uring enabled, particularly those utilizing zero-copy receive functionality for high-performance networking applications.

Technical summary

The vulnerability exists in the io_uring zero-copy receive (zcrx) implementation. The function `io_free_rbuf_ring()` accesses a `struct user_struct` pointer after `io_zcrx_ifq_free()` has already called `put_user_struct()` on it, resulting in a use-after-free condition. This can lead to memory corruption or potentially local privilege escalation. The fix ensures proper ordering of reference count operations during ring buffer teardown.

Defensive priority

high

Recommended defensive actions

  • Apply kernel patches from stable tree commits referenced in CVE record
  • Prioritize patching systems using io_uring with zero-copy receive (zcrx) functionality
  • Monitor for stable kernel updates containing the fix
  • Review custom io_uring applications for zcrx usage
  • Consider disabling io_uring or zcrx features if patching is not immediately feasible and functionality is not required

Evidence notes

CVE published 2026-05-27T14:17:17.080Z; modified 2026-05-27T14:48:03.013Z. Kernel commit references confirm fix in stable tree.

Official resources

2026-05-27