CVE-2026-31484
Published: 22 April 2026
Summary
CVE-2026-31484 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Credential Access (T1212); ranked at the 4.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-31484 is an out-of-bounds read vulnerability in the Linux kernel's io_uring subsystem, specifically within the __io_uring_show_fdinfo() function. The issue affects rings configured with IORING_SETUP_SQE_MIXED using 128-byte submission queue entries (SQEs). During iteration over pending SQEs, the code incorrectly checks for wrap-around at the end of the sq_sqes array by testing (++sq_head & sq_mask) == 0. This fails because sq_head increments only on 128-byte SQEs, allowing the actual array index sq_idx = (i + sq_head) & sq_mask to reach sq_mask (the last slot) without triggering the check, leading to an out-of-bounds read. The vulnerability is classified under CWE-125 with a CVSS v3.1 base score of 7.1 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H).
A local attacker with low privileges can exploit this vulnerability by triggering the fdinfo exposure for an io_uring instance, potentially reading sensitive kernel memory out-of-bounds or causing a denial of service through kernel crash. The low attack complexity and lack of user interaction make it feasible for unprivileged processes to achieve high-impact confidentiality violations or availability disruptions without privilege escalation or scope changes.
Mitigation requires updating to a patched Linux kernel version incorporating the fixes from the referenced stable commits: 5170efd9c344c68a8075dcb8ed38d3f8a60e7ed4 and ba21ab247a5be5382da7464b95afbe5f0e9aa503, available at git.kernel.org. These patches correct the wrap check by directly validating sq_idx while preserving sq_head increments to skip the second half of 128-byte SQEs on subsequent iterations.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24847
Vulnerability details
In the Linux kernel, the following vulnerability has been resolved: io_uring/fdinfo: fix OOB read in SQE_MIXED wrap check __io_uring_show_fdinfo() iterates over pending SQEs and, for 128-byte SQEs on an IORING_SETUP_SQE_MIXED ring, needs to detect when the second half of the…
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SQE would be past the end of the sq_sqes array. The current check tests (++sq_head & sq_mask) == 0, but sq_head is only incremented when a 128-byte SQE is encountered, not on every iteration. The actual array index is sq_idx = (i + sq_head) & sq_mask, which can be sq_mask (the last slot) while the wrap check passes. Fix by checking sq_idx directly. Keep the sq_head increment so the loop still skips the second half of the 128-byte SQE on the next iteration.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
OOB kernel memory read enables credential access via sensitive data exposure (T1212); kernel crash path directly supports DoS via system exploitation (T1499.004). Local low-priv trigger matches both without requiring escalation or remote access.
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Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mitigates the out-of-bounds read vulnerability by requiring identification, reporting, and timely correction of the specific flaw in the io_uring fdinfo function via kernel patching.
Employs vulnerability scanning to identify the CVE-2026-31484 flaw in the Linux kernel io_uring subsystem, enabling proactive remediation before exploitation.
Provides memory protections such as randomization and non-executable regions that mitigate the impact of the out-of-bounds read leaking sensitive kernel memory.