PatchSiren cyber security CVE debrief

CVE-2026-5066 zephyrproject-rtos CVE debrief

CVE-2026-5066 is a potential out-of-bounds write/read vulnerability in the TLS socket connect path of the network sockets subsystem. The vulnerability occurs when the TLS session cache is enabled, and the tls_session_store() and tls_session_restore() functions memcpy the caller-supplied address into a fixed-size buffer using the caller-controlled addrlen value without validating it against the destination size. This can lead to a crash and denial of service, and potentially to arbitrary code execution.

Vendor: zephyrproject-rtos
Product: Zephyr
CVSS: MEDIUM 6.3
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-06-04
Original CVE updated: 2026-06-05
Advisory published: 2026-06-04
Advisory updated: 2026-06-05

Who should care

Developers and users of the Zephyr RTOS, as well as anyone using the affected network sockets subsystem.

Technical summary

The vulnerability is caused by a lack of validation of the addrlen value against the destination size in the tls_session_store() and tls_session_restore() functions. This allows an attacker to pass an addrlen larger than sizeof(struct net_sockaddr), causing the memcpy to read and write past the end of the address memory used by the TLS session cache.

Defensive priority

MEDIUM

Recommended defensive actions

Apply patches or updates provided by the vendor to fix the vulnerability.
Disable the TLS session cache if not required.
Validate user input to prevent passing an addrlen larger than sizeof(struct net_sockaddr).

Evidence notes

The vulnerability was reported by [email protected] and is tracked under GHSA-wgrc-jrf6-24f3.

Official resources

CVE-2026-5066 was published on 2026-06-04T21:16:30.907Z and modified on 2026-06-05T19:16:34.743Z.