CVE-2023-0458

What it actually does

Speculative pointer dereference in do_prlimit() allows a local attacker to control the resource argument and perform pointer arithmetic on the rlim variable, leaking kernel memory contents via side channels.

Why it matters to the business

Local users on unpatched Linux systems may expose sensitive kernel data, raising the risk of information theft that could aid further attacks or data breaches on servers and endpoints.

How an attack unfolds

An attacker with local access invokes do_prlimit() with a crafted resource value that triggers speculative execution, using the resulting pointer arithmetic on rlim to leak kernel memory contents through observable side effects.

How to fix it

Upgrade the Linux kernel past version 6.1.8 or apply commit 739790605705ddcf18f21782b9c99ad7d53a8c11 (or the equivalent 93f875a8526a291005e7f38478079526c843cbec in affected trees). Rebuild and reboot with the patched kernel; verify the version after deployment.

How to confirm the fix worked

Confirm the running kernel version is at or above the fixed release; review kernel source or changelog for the referenced commit; test that do_prlimit() no longer permits the speculative leak under controlled conditions.

Typical attack path

1. Gain local user access on a vulnerable Linux system
2. Call do_prlimit() with a maliciously chosen resource argument
3. Trigger speculative execution to dereference a controlled pointer
4. Observe side-channel leakage of rlim variable contents
5. Extract and analyze leaked kernel memory for sensitive data

How to detect it

Examine system call logs or audit trails for repeated or anomalous prlimit invocations from unprivileged processes; look for side-channel timing artifacts or unexpected kernel memory access patterns in performance or debug logs, though direct indicators are limited without active exploitation.

What your security team should do

• Immediately identify all Linux systems running kernels before 6.1.8 and schedule patching
• Prioritize upgrades on internet-facing or multi-tenant hosts due to local information disclosure risk
• Monitor vendor advisories for backported fixes in distribution kernels
• Review local access controls and limit untrusted user accounts until patches are applied