# CVE-2026-15892: Heap memory leak in mcumgr settings-management handlers on access-hook rejection leads to denial of service

> Attackers can exhaust kernel heap memory via rejected mcumgr settings requests, causing denial of service in Zephyr RTOS devices.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-rq68-wgv4-hcq3

## What is CVE-2026-15892?

CVE-2026-15892 is a medium-severity denial of service vulnerability in zephyrproject zephyr, published on 13 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The mcumgr SMP settings-management group handlers settings_mgmt_read(), settings_mgmt_write(), and settings_mgmt_delete() in subsys/mgmt/mcumgr/grp/settings_mgmt/src/settings_mgmt.c allocate a key_name buffer (and, for read, a data buffer) via k_malloc() when CONFIG_MCUMGR_GRP_SETTINGS_BUFFER_TYPE_HEAP is enabled, relying on the end: label to k_free() them. When CONFIG_MCUMGR_GRP_SETTINGS_ACCESS_HOOK is also enabled and the application access hook rejects a request by returning status MGMT_CB_ERROR_RC, the handler executed return ret_rc; directly, bypassing end: and leaking the heap allocation on every rejected request.

The settings handlers are reachable over the unauthenticated SMP transport (Bluetooth LE, UART, or UDP, depending on product configuration). The access hook is the mechanism applications use to deny unauthorized settings access, and MGMT_CB_ERROR_RC is a common rejection style, so an attacker who can send settings read/write/delete commands that the hook rejects triggers a heap leak on each attempt.

Because the leaked memory is never reclaimed until reboot, a sustained stream of rejected requests monotonically exhausts the kernel heap until k_malloc() fails, denying mcumgr service and impacting any other heap consumer on the device — a denial of service. The impact is availability-only; there is no memory corruption or information disclosure. Only configurations that select the heap buffer type, enable the access hook, and register a hook that returns MGMT_CB_ERROR_RC are affected (the default stack buffer type cannot leak).

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-15892?


## How do I fix CVE-2026-15892?

No fix has been published for CVE-2026-15892 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-15892 being exploited?

There is no known exploitation of CVE-2026-15892 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-15892 and fix it if it is affected.

What it is: CVE-2026-15892 is a medium-severity denial of service vulnerability in zephyrproject zephyr, published on 13 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-15892 in the wild and no public exploit code.

Affected product: zephyrproject zephyr. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-15892/ (Markdown: https://insights.sbomify.com/CVE-2026-15892/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-15892
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15892
- OSV: https://osv.dev/vulnerability/CVE-2026-15892

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-15892/
Summaries are generated and may contain mistakes; the official description above is the record.