VulnerabilityPublished 28 Sep 2026Updated 30 Sep 2026

CVE-2026-18417: zephyrproject zephyr · Memory-safety

Affects zephyrproject zephyrSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 4.4.2 when convenient.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.4.2

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade zephyrproject zephyr to 4.4.2.

Affected software

Product	Affected	Fixed in
zephyrprojectzephyr	Affected >=4.3.0 <4.4.2	Fixed in 4.4.2
GitHubzephyr`pkg:github/zephyr`Other threats	Affected >=4.3.0 <4.4.2	Fixed in 4.4.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Zephyr versions 4.3.1 and later, including 4.4.x and 4.4.2, which properly separate error storage from the user_data field and clear the accept callback after error handling. Users should upgrade to these fixed versions to mitigate the vulnerability. No additional mitigation is required as the issue is addressed by the official fix.

Description

CVE-2026-18417 is a memory-safety vulnerability in the Zephyr project's native BSD-socket layer affecting versions 4.3.0 up to but not including 4.4.2. The issue arises from improper handling of asynchronous socket errors by storing error codes in a field expected to hold a pointer, leading to wild-pointer dereferences during repeated network interface down events. This results in a kernel fatal error causing denial of service (device crash or reset) but does not allow attacker-controlled memory corruption. The vulnerability requires an attacker to repeatedly cause link-down events, such as disrupting a wireless link or having local/physical access. Later versions fix this by separating error storage from the user_data field and preventing stale error propagation.

Impact

The vulnerability causes a denial of service via kernel fatal errors (device crash or reset) when a listening TCP socket remains open across repeated network interface down events. It does not allow attacker-controlled memory corruption or data leakage. Exploitation requires the ability to repeatedly cause link-down events, which may be feasible for adjacent attackers disrupting wireless links or those with local/physical access.

Summary

The vulnerability involves the native BSD-socket layer in Zephyr where asynchronous socket errors are type-punned into the void user_data field of struct net_context. This field is also used by the network stack to store a parent context pointer for listening TCP sockets. When a network interface goes down, the accept callback is invoked with an error code stored in user_data, which is then incorrectly dereferenced as a pointer on repeated interface-down events in version 4.3.0. This causes wild-pointer accesses leading to kernel fatal errors and denial of service. Versions 4.3.1 and later include fixes that clear the accept callback after error handling and store errors in a dedicated sock_error field, preventing stale error propagation and kernel crashes.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Oct 2026, 20:59 UTC

Technical details

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