Quick answers
- Is CVE-2026-19739 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-19739 being exploited in the wild.
- How severe is CVE-2026-19739?
- Medium severity, with a CVSS score of 6.5, published 11 October 2026.
- Which products and versions are affected?
- Zephyr Project Zephyr OS vulnerable versions unspecified in advisory.
- Is there a fix for CVE-2026-19739?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-19739 attacked?
- It is attacked from the adjacent network, in an operating system.
- Am I affected by CVE-2026-19739?
- Check whether you run Zephyr Project Zephyr OS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability exists in ull_llcp_conn_upd.c where a retained RX node is not properly released when the connection update procedure receives an invalid PDU while waiting for the update instant. An attacker sends a valid LL_CONNECTION_UPDATE_IND to trigger the procedure, then sends an invalid LL Control PDU (such as LL_LENGTH_REQ) before the instant arrives, causing the procedure to take an error path that fails to release the retained node. Repeating this sequence exhausts the fixed-size RX buffer pool, causing subsequent link-layer receive operations to operate on NULL pointers.
Affected products
- Zephyr Project Zephyr OS vulnerable versions unspecified in advisory
Timeline
- 2026-10-11: disclosed