# CVE-2026-17251: Unauthenticated Denial of Service via Null Pointer Dereference in HTTP Request Parsing

> An unauthenticated remote attacker can crash the HTTP service on TP-Link TL-MR6400 v7 routers by sending a malformed session cookie header.

- **Severity:** High 7.1 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **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:** 21 Aug 2026
- **Updated:** 21 Aug 2026
- **Also known as:** GHSA-cfmx-mjrq-52xj

## What is CVE-2026-17251?

CVE-2026-17251 is a high-severity vulnerability in TP-Link Systems Inc. TL-MR6400 v7.0, published on 21 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A NULL
pointer dereference vulnerability exists in the HTTP request parsing
functionality of 
TL-MR6400 v7. An unauthenticated remote attacker can
trigger the vulnerability by sending a specially crafted HTTP request
containing a malformed session cookie header. 

Successful
exploitation may cause the HTTP service process to crash, resulting in a
denial-of-service condition and temporary loss of management or CGI
functionality until service recovery.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-17251?


## How do I fix CVE-2026-17251?

No fix has been published for CVE-2026-17251 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-17251 being exploited?

There is no known exploitation of CVE-2026-17251 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-17251 and fix it if it is affected.

What it is: CVE-2026-17251 is a high-severity vulnerability in TP-Link Systems Inc. TL-MR6400 v7.0, published on 21 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-2026-17251 in the wild and no public exploit code.

Affected product: TP-Link Systems Inc. TL-MR6400 v7.0. 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-2026-17251/ (Markdown: https://insights.sbomify.com/CVE-2026-17251/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-17251
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-17251
- OSV: https://osv.dev/vulnerability/CVE-2026-17251

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-17251/
Summaries are generated and may contain mistakes; the official description above is the record.