Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-23066 is a high-severity Uncontrolled Recursion (CWE-674) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and SC-5 (Denial-of-service Protection) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-23066 is a vulnerability in the Linux kernel's RxRPC implementation, specifically within the rxrpc_recvmsg() function. When recvmsg() fails due to the MSG_DONTWAIT flag but the call at the front of the recvmsg queue has its mutex locked, the function unconditionally requeues the call, even if it is already queued—such as after a prior MSG_PEEK operation or requeue by the I/O thread. This behavior corrupts the recvmsg queue, potentially leading to use-after-free (UAF) conditions or reference count underruns. An additional issue with MSG_PEEK not dequeuing calls but incorrectly notifying the socket is also addressed.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low attack complexity (AC:L) and no user interaction (UI:N) in an unprivileged scope (S:U). Successful exploitation could result in high impacts across confidentiality, integrity, and availability (C:H/I:H/A:H), with a CVSS v3.1 base score of 7.8. The attacker could leverage the queue corruption to trigger UAFs or refcount bugs, potentially enabling arbitrary code execution or kernel crashes.
Mitigation involves applying the upstream kernel patches provided in the referenced stable commits: 0464bf75590da75b8413c3e758c04647b4cdb3c6, 2c28769a51deb6022d7fbd499987e237a01dd63a, 930114425065f7ace6e0c0630fab4af75e059ea8, and cf969bddd6e69c5777fa89dc88402204e72f312a. These fixes ensure calls are only requeued if not already on the queue (moving them to the front if present), properly handle references on non-queued calls, and correct MSG_PEEK socket notifications when not all queue data is consumed. Security practitioners should update affected Linux kernels to versions incorporating these commits.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-5478
Vulnerability Data
In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix recvmsg() unconditional requeue If rxrpc_recvmsg() fails because MSG_DONTWAIT was specified but the call at the front of the recvmsg queue already has its mutex locked, it requeues the…
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call - whether or not the call is already queued. The call may be on the queue because MSG_PEEK was also passed and so the call was not dequeued or because the I/O thread requeued it. The unconditional requeue may then corrupt the recvmsg queue, leading to things like UAFs or refcount underruns. Fix this by only requeuing the call if it isn't already on the queue - and moving it to the front if it is already queued. If we don't queue it, we have to put the ref we obtained by dequeuing it. Also, MSG_PEEK doesn't dequeue the call so shouldn't call rxrpc_notify_socket() for the call if we didn't use up all the data on the queue, so fix that also.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Input validation can reject or constrain data that would otherwise drive unbounded recursive calls.
DoS protection mechanisms limit the resource-exhaustion impact of uncontrolled recursion without eliminating the flaw.
System monitoring can observe anomalous resource consumption that signals runaway recursion after it begins.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly prevent coding errors such as missing recursion limits or termination conditions.
Runtime monitoring of compute resources can detect excessive consumption caused by uncontrolled recursion.
Vulnerability identification processes can discover and record uncontrolled recursion flaws before deployment.
Capacity monitoring and resource provisioning can absorb or limit the impact of runaway recursion.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect excessive recursion via static analysis or fuzzing.
Secure development life cycle requires controls that prevent uncontrolled recursion through design and code review.
Application security requirements can mandate recursion limits or stack-depth checks.
Secure system architecture principles include resource-management and input-validation rules that limit recursion.
Secure coding standards directly prohibit or constrain recursive constructs that could exhaust stack or memory.
Capacity management includes monitoring and limits that mitigate resource exhaustion from runaway recursion.