# CVE-2026-55490: OpenWrt: EAD Integer Underflow → Pre-Auth Denial of Service

> An unauthenticated attacker can crash the Emergency Access Daemon via a crafted UDP packet due to an integer underflow, causing denial of service.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Jul 2026
- **Updated:** 8 Jul 2026
- **Also known as:** GHSA-9558-77jp-g3fw

## What is CVE-2026-55490?

CVE-2026-55490 is a medium-severity vulnerability in Openwrt Openwrt, published on 7 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

OpenWrt is a Linux operating system targeting embedded devices. Before v25.12.5, an integer underflow in handle_send_a() of the Emergency Access Daemon allows any unauthenticated attacker on the local network to crash the daemon by sending a single crafted UDP packet. The message length underflows before a bounds check and is then passed to memcpy as a very large size. This issue is fixed v25.12.5.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound))

## Which versions are affected by CVE-2026-55490?

It affects 1 product.


Products: Openwrt Openwrt.

## How do I fix CVE-2026-55490?

No fix has been published for CVE-2026-55490 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-55490 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55490 exists.

## Other vulnerabilities in Openwrt Openwrt

- [CVE-2020-28951](https://insights.sbomify.com/CVE-2020-28951/): Use after free in n/a (critical 9.8)
- [CVE-2026-62948](https://insights.sbomify.com/CVE-2026-62948/): Cross-site scripting in openwrt (critical 9.6)
- [CVE-2026-30871](https://insights.sbomify.com/CVE-2026-30871/): OpenWrt Project has Stack-based Buffer Overflow in DNS PTR Query (critical 9.5)
- [CVE-2026-30872](https://insights.sbomify.com/CVE-2026-30872/): OpenWrt Project has a Stack-based Buffer Overflow vulnerability via IPv6 reverse DNS lookup (critical 9.5)
- [CVE-2021-28961](https://insights.sbomify.com/CVE-2021-28961/): Command injection in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55490 and fix it if it is affected.

What it is: CVE-2026-55490 is a medium-severity vulnerability in Openwrt Openwrt, published on 7 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55490 exists.

Affected product: Openwrt Openwrt. 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-2026-55490/ (Markdown: https://insights.sbomify.com/CVE-2026-55490/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55490
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55490
- OSV: https://osv.dev/vulnerability/CVE-2026-55490

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55490/
Summaries are generated and may contain mistakes; the official description above is the record.