# CVE-2026-11812: UpdateHub: race condition on shared context causes out-of-bounds write and DoS

> A race condition in Zephyr's UpdateHub subsystem allows local attackers to cause an out-of-bounds write and denial of service.

- **Severity:** Low 2.5 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Aug 2026
- **Updated:** 31 Aug 2026
- **Also known as:** GHSA-vprh-rff6-46xp

## What is CVE-2026-11812?

CVE-2026-11812 is a low-severity vulnerability in zephyrproject zephyr, published on 10 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The UpdateHub management subsystem (subsys/mgmt/updatehub/updatehub.c) drives every update operation through a single file-scope ctx structure that holds the CoAP block context, payload buffer, status code, socket, and a one-element poll-fd array fds[1]. Access to ctx was not serialized, and prepare_fds() wrote ctx.fds[ctx.nfds] and incremented ctx.nfds with no bounds check.

Two independent paths mutate ctx concurrently: the background autohandler running on the system workqueue, and user-triggered operations reached through the updatehub run shell command, direct API calls, or — since the operations are exposed as syscalls — userspace threads. When a second flow enters prepare_fds() while ctx.nfds is already 1, the write lands one element past the array; by struct layout it overlaps the adjacent ctx.sock/ctx.nfds members. More broadly, the unsynchronized sharing lets two flows interleave connection setup and teardown, double-closing a socket descriptor or scribbling the shared buffers.

The result is corruption of the update subsystem's internal state and denial of service of the firmware-update path; the out-of-bounds write is contained within the ctx structure and there is no demonstrated path to memory outside it or to code execution. Triggering requires a local actor able to invoke update operations (or, with CONFIG_USERSPACE, an unprivileged userspace thread) and to win a timing race against the background handler; remote peers cannot control the race timing. The fix serializes the entry points with a mutex and adds a bounds check to prepare_fds().

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-11812?


## How do I fix CVE-2026-11812?

No fix has been published for CVE-2026-11812 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-11812 being exploited?

There is no known exploitation of CVE-2026-11812 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11812 and fix it if it is affected.

What it is: CVE-2026-11812 is a low-severity vulnerability in zephyrproject zephyr, published on 10 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-11812 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-2026-11812/ (Markdown: https://insights.sbomify.com/CVE-2026-11812/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11812
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11812
- OSV: https://osv.dev/vulnerability/CVE-2026-11812

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-11812/
Summaries are generated and may contain mistakes; the official description above is the record.