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Zephyr CVE-2026-10666

| EUVDEUVD-2026-43243 CRITICAL
Out-of-bounds Write (CWE-787)
2026-07-12 zephyr
9.8
CVSS 3.1 · NVD
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Severity by source

Vendor (zephyr) PRIMARY
HIGH
qualitative
NVD
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from Vendor (zephyr).

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

6
Source Code Evidence Fetched
Jul 17, 2026 - 13:45 vuln.today
Analysis Updated
Jul 17, 2026 - 13:45 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Jul 17, 2026 - 13:37 vuln.today
cvss_changed
Severity Changed
Jul 17, 2026 - 13:37 NVD
HIGH CRITICAL
CVSS changed
Jul 17, 2026 - 13:37 NVD
8.1 (HIGH) 9.8 (CRITICAL)
Analysis Generated
Jul 12, 2026 - 17:24 vuln.today

DescriptionNVD

parse_ipv4() in subsys/net/ip/utils.c (reached via net_ipaddr_parse() for strings of the form "a.b.c.d:port") copies the port substring into a fixed 17-byte stack buffer (char ipaddr[NET_IPV4_ADDR_LEN + 1]) using a length of str_len - end - 1, where str_len is the full, unbounded input length and end is only the (<=15-byte) offset of the ':' delimiter. Because the destination size is never consulted, a crafted address string with a long suffix after the colon (e.g. "1.2.3.4:" followed by hundreds of bytes) causes an out-of-bounds stack write whose length and contents are fully attacker-controlled (memcpy of the suffix plus a trailing NUL), enabling memory corruption and at minimum a denial of service, and potentially control-flow hijack. The parser is reached from the standard socket API (zsock_getaddrinfo / literal-address resolution), DNS server-string configuration, and the eswifi Wi-Fi co-processor DNS-response path, so an application that resolves a network-influenced address string is exposed. The bug was introduced when the parser was added (Zephyr v1.9.0) and shipped in all releases through v4.4.0. The fix removes the unbounded copy and validates the port length before copying into a small dedicated buffer. Note: the equivalent IPv6 "[addr]:port" path in parse_ipv6() retains the same unbounded copy at this commit and remains a separate, still-reachable instance of the defect.

AnalysisAI

Stack out-of-bounds write in the Zephyr RTOS network IP-parsing utility (parse_ipv4() in subsys/net/ip/utils.c) lets a crafted "a.b.c.d:port" address string with an overlong post-colon suffix overflow a 17-byte stack buffer with fully attacker-controlled length and contents, affecting Zephyr 1.9.0 through 4.4.0. Any application that resolves a network-influenced address string via the standard socket API (zsock_getaddrinfo/literal resolution), DNS server-string configuration, or the eswifi Wi-Fi DNS-response path is exposed, yielding at minimum denial of service and potentially control-flow hijack. No public exploit identified at time of analysis and it is not listed in CISA KEV; SSVC records proof-of-concept maturity and EPSS is low at 0.35%.

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CVE-2026-10666 vulnerability details – vuln.today

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