CVE-2026-5066: A potential out-of-bounds write/read exists in the TLS socket connect path of the network sockets subsystem (s

Q: How do I fix CVE-2026-5066?

zephyr: upgrade to newer than 4.3.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-5066 being exploited?

CVE-2026-5066 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-5066 affect?

CVE-2026-5066 affects zephyr. Severity is medium (CVSS 6.3). 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

Q: How urgent is CVE-2026-5066?

Priority 33/100. Public exploit reference

Routine

MEDIUM 6.3UPGRADE

CVE-2026-5066 is a medium-severity flaw (CVSS 6.3) affecting zephyr. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 pa

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 75%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-06-04
Last modified	2026-10-15

Publisher (CNA): Zephyr Project · Vendor: zephyrproject

Last updated 2026-10-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-04 21:16 UTCPublished CVE record published
2026-10-15 23:17 UTCUpdated Record last modified

zephyrproject zephyr UPGRADE

Affected: <= 4.3.0

Fixed in: newer than 4.3.0

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-5066?

zephyr: upgrade to newer than 4.3.0. Exact commands for each OS are on this page.

Is CVE-2026-5066 being exploited?

CVE-2026-5066 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-5066 affect?

CVE-2026-5066 affects zephyr. Severity is medium (CVSS 6.3). 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

How urgent is CVE-2026-5066?

Priority 33/100. Public exploit reference

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References

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