CVE-2026-12234 is a high-severity (CVSS 7.8) CWE-367 vulnerability. O3 Security confirms whether CVE-2026-12234 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
The userspace syscall verifiers z_vrfy_zsock_sendmsg() and z_vrfy_zsock_recvmsg() in subsys/net/lib/sockets/sockets.c snapshot the caller-supplied struct net_msghdr into a kernel-side…
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-12234.
Description
The userspace syscall verifiers z_vrfy_zsock_sendmsg() and z_vrfy_zsock_recvmsg() in subsys/net/lib/sockets/sockets.c snapshot the caller-supplied struct net_msghdr into a kernel-side copy with k_usermode_from_copy(), but then re-read the still-live user struct for subsequent decisions. The kernel iovec shadow buffer is sized from one read of msg->msg_iovlen, while the population loop is bounded by a second, live read of the same field.
Because msg points into ordinary user memory, a cooperating second thread in the same memory domain can inflate msg->msg_iovlen in the window between the sizing read and the loop test (a classic double-fetch / TOCTOU). The population loop then iterates past the number of net_iovec slots actually allocated, writing attacker-influenced iov_base/iov_len values beyond the end of the kernel-heap shadow buffer. The recvmsg verifier has the same defect on both its inbound and result write-back loops.
The code is reachable from an unprivileged user thread whenever CONFIG_USERSPACE is enabled and the zsock_sendmsg/zsock_recvmsg syscalls are available. A successful race corrupts kernel-managed heap memory across the user-to-kernel privilege boundary, yielding a local privilege-escalation primitive or, at minimum, a kernel-fault denial of service. The fix copies the header once and derives every size, bound, and gate from the snapshot, copying each iovec entry atomically so its base and length can no longer be raced apart.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-12234 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-12234 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-12234. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-12234 in your dependencies?
O3 detects CVE-2026-12234 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.