CVE-2026-45866 - In the Linux kernel, the following vulnerability has been resolved: serial: caif: fix use-after-free in caif_s

CVE-2026-45866 + In the Linux kernel, the following vulnerability has been resolved: serial: caif: fix use-after-free in caif_s + High + 2026-05-27

One-sentence business risk

A small malicious input can exhaust workers or crash services, creating a customer-visible availability incident.

Research notes

  • Root cause: In the Linux kernel, the following vulnerability has been resolved: serial: caif: fix use-after-free in caif_serial ldisc_close() There is a use-after-free bug in caif_serial where handle_tx() may access ser->tty after the tty has been freed.
  • Affected versions: before unregister_netdevice() because ser is embedded in netdev’s private data and will be freed along with netdev (needs_free_netdev = true).
  • Fixed / safe versions: Vendor-fixed release or mitigation named by the upstream advisory.
  • Public exploit / PoC signal: the consulted NVD/GHSA/vendor sources describe the trigger class; treat it as reproducible until patched.
  • CVSS: 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Exact vulnerable code pattern

parse_or_buffer(untrusted_payload)  # unbounded size, time, or concurrency

Fixed / mitigated code pattern

enforce max bytes, frame counts, parser depth, request timeouts, and worker limits

Dependency or runtime update:

rg -n "affected component|CVE-2026-45866" .
# update affected runtime/product to Vendor-fixed release or mitigation named by the upstream advisory

Step-by-step integration guide

  1. Inventory affected component across source, lockfiles, SBOMs, container images, CI images, and deployment manifests.
  2. Upgrade to Vendor-fixed release or mitigation named by the upstream advisory or apply the exact vendor patch referenced below.
  3. Replace the vulnerable dos pattern with the fixed pattern and fail closed on malformed input.
  4. Add a regression test that exercises the advisory trigger and proves the request is rejected, bounded, or authorized.
  5. Deploy through canary, monitor security logs and resource metrics, then remove temporary edge blocks only after all runtimes are fixed.

Alternative mitigations

  • Disable the vulnerable feature path while the package/runtime update rolls out.
  • Add WAF or reverse-proxy rules for traversal tokens, prototype-polluting keys, oversized frames, shell metacharacters, or unauthenticated tool calls matching the trigger class.
  • Restrict internal egress, rotate exposed secrets, and revoke affected tokens/keys if the vulnerability can disclose config, logs, JWT secrets, proxy credentials, or PKI material.
  • For admin/API authorization issues, temporarily require elevated roles and explicit ownership checks at the gateway.

Detection signature

id: cve-2026-45866-in-the-linux-kernel-the-following-vulnerability-
source: NVD
dependency_or_product: "affected component"
affected: "before unregister_netdevice() because ser is
embedded in netdev's private data and will be freed along with netdev
(needs_free_netdev = true)"
fixed: "Vendor-fixed release or mitigation named by the upstream advisory"
signals:
  - "dos"
  - "../"
  - "__proto__"
  - "tools/call"
  - "wp_ajax_nopriv"
  - "pickle.loads"
  - "shell command construction"
action: "upgrade, add regression test, and verify deploy artifact"

Copy-paste skill

You are remediating CVE-2026-45866 (In the Linux kernel, the following vulnerability has been resolved: serial: caif: fix use-after-free in caif_s) in this repository.

Find every affected dependency, runtime, image, service configuration, and reachable code path. Upgrade or patch to Vendor-fixed release or mitigation named by the upstream advisory. Replace the vulnerable dos pattern with a fail-closed implementation, add a regression test for the trigger shape, and update deployment/SBOM artifacts. If this repository does not control the affected runtime, create TRIAGE.md naming the owner, affected version, fixed version, and blocking decision.

Keywords, affected tech stack, and revenue tags

  • Keywords: CVE-2026-45866, dos, affected component, NVD.
  • Affected tech stack: general.
  • Revenue tags: sellable_to_fintech, enterprise_blocker, high_priority_sla.

References