VulnerabilityPublished 13 Sep 2026

CVE-2026-15892: zephyrproject zephyr · Dos

Affects zephyrproject zephyrSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to 4.4.2 when convenient.

Data as of 29 Oct 2026, 07:15 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.4.2

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

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

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
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: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 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 29 Oct 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 >=3.5.0 <4.4.2	Fixed in 4.4.2
GitHubzephyr`pkg:github/zephyr`Other threats	Affected >=3.5.0 <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

If you cannot patch yet, avoid configurations that enable both CONFIG_MCUMGR_GRP_SETTINGS_BUFFER_TYPE_HEAP and CONFIG_MCUMGR_GRP_SETTINGS_ACCESS_HOOK with hooks that reject requests using MGMT_CB_ERROR_RC. Alternatively, use the default stack buffer type which is not vulnerable to this leak.

Description

CVE-2026-15892 is a denial of service vulnerability in the Zephyr project's mcumgr SMP settings-management handlers. When configured to use heap buffers and an access hook that rejects requests, the handlers leak heap memory on each rejected request. This leak eventually exhausts the kernel heap, causing k_malloc() failures and service denial. The vulnerability affects versions from 3.5.0 up to but not including 4.4.2. The impact is limited to availability with no memory corruption or information disclosure.

Impact

An attacker able to send settings read/write/delete commands that are rejected by the access hook can cause a heap memory leak on each attempt. Over time, this exhausts the kernel heap, causing k_malloc() failures and denial of service of the mcumgr service and other heap consumers on the device. There is no impact on confidentiality or integrity, only availability is affected.

Summary

In Zephyr's mcumgr SMP settings-management group handlers (settings_mgmt_read, settings_mgmt_write, settings_mgmt_delete), when CONFIG_MCUMGR_GRP_SETTINGS_BUFFER_TYPE_HEAP and CONFIG_MCUMGR_GRP_SETTINGS_ACCESS_HOOK are enabled, rejected requests that return MGMT_CB_ERROR_RC bypass the cleanup label 'end:', causing heap memory allocated via k_malloc() to leak. These handlers are accessible over unauthenticated SMP transports such as Bluetooth LE, UART, or UDP. Repeated rejected requests cause a monotonic heap exhaustion leading to denial of service by preventing further allocations. The vulnerability affects Zephyr versions >=3.5.0 and <4.4.2.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 21 Sep 2026, 01:07 UTC

Technical details

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