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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
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-06-16
Advisory published
2026-05-27
Advisory updated
2026-06-16

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.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-45995 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-45995

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-45995 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-45995

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/0fcccfd87152f957fa8312b841f6efef42a05a20

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9feb88eeda6d288f93fcfb6bca563f89e316479d

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.