# CVE-2026-42800: Deference after null check in ims_client sip

> A null pointer dereference in the IMS client SIP module of ASR Lapwing Linux allows attackers to cause a denial of service.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Apr 2026
- **Updated:** 30 Apr 2026
- **Also known as:** GHSA-6438-jwc8-2c68

## What is CVE-2026-42800?

CVE-2026-42800 is a high-severity vulnerability in ASR Lapwing_Linux, published on 30 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

NULL pointer dereference vulnerability in ASR1903 in ASR Lapwing_Linux on Linux (ims_client modules) allows Pointer Manipulation.

 This vulnerability is associated with program files sip/utils/src/sipuri.c.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-42800?

It affects 2 products.


Products: Asrmicro Asr1901 Firmware, Asrmicro Asr1903 Firmware.

## How do I fix CVE-2026-42800?

No fix has been published for CVE-2026-42800 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42800 being exploited?

There is no known exploitation of CVE-2026-42800 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42800 and fix it if it is affected.

What it is: CVE-2026-42800 is a high-severity vulnerability in ASR Lapwing_Linux, published on 30 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42800 in the wild and no public exploit code.

Affected product: ASR Lapwing_Linux. 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-2026-42800/ (Markdown: https://insights.sbomify.com/CVE-2026-42800/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42800
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42800
- OSV: https://osv.dev/vulnerability/CVE-2026-42800

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42800/
Summaries are generated and may contain mistakes; the official description above is the record.