CVE-2026-5066
CVE-2026-5066 is a medium-severity vulnerability in Zephyrproject Zephyr with a CVSS 3.x base score of 6.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.
Key facts
- Severity: Medium (CVSS 3.x base score 6.3)
- EPSS exploit prediction: 0% (12th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-34324
- Weakness: CWE-787
- Affected product: Zephyrproject Zephyr
- Published:
- Last modified:
Description
A potential out-of-bounds write/read exists in the TLS socket connect path of the network sockets subsystem (subsys/net/lib/sockets/sockets_tls.c). When the TLS session cache is enabled, tls_session_store() and tls_session_restore() memcpy the caller-supplied address into a fixed-size buffer using the caller-controlled addrlen value without validating it against the destination size. struct net_sockaddr is an opaque type, so an application can pass an addrlen larger than sizeof(struct net_sockaddr) (for example 128 bytes into a 24-byte stack buffer), causing the memcpy to read and write past the end of the address memory used by the TLS session cache. This out-of-bounds write can lead to a crash and denial of service, and potentially to arbitrary code execution.
Frequently asked questions
- What is CVE-2026-5066?
- A potential out-of-bounds write/read exists in the TLS socket connect path of the network sockets subsystem (subsys/net/lib/sockets/sockets_tls.c). When the TLS session cache is enabled, tls_session_store() and tls_session_restore() memcpy the caller-supplied address into a fixed-size buffer using the caller-controlled addrlen value without validating it against the destination size. struct net_sockaddr is an opaque type, so an application can pass an addrlen larger than sizeof(struct net_sockaddr) (for example 128 bytes into a 24-byte stack buffer), causing the memcpy to read and write past the end of the address memory used by the TLS session cache. This out-of-bounds write can lead to a crash and denial of service, and potentially to arbitrary code execution.
- How severe is CVE-2026-5066?
- CVE-2026-5066 has a CVSS 3.x base score of 6.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
- Is CVE-2026-5066 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-5066?
- CVE-2026-5066 affects Zephyrproject Zephyr. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-5066?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-5066 have an EU (EUVD) identifier?
- Yes. CVE-2026-5066 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34324.
- When was CVE-2026-5066 published?
- CVE-2026-5066 was published on 2026-06-04 and last updated on 2026-07-08.
References
Affected products (1)
- cpe:2.3:o:zephyrproject:zephyr:*:*:*:*:*:*:*:*
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