# CVE-2026-12495: Stack-Based Buffer Overflow in the Mercusys MB115-4G

> Unauthenticated attackers can crash the web administration service of Mercusys MB115-4G routers via a stack buffer overflow in the login endpoint.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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:** 27 Jul 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-f8cq-j6x7-pfpx

## What is CVE-2026-12495?

CVE-2026-12495 is a medium-severity memory corruption vulnerability in Mercusys MB115-4G, published on 27 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Denial-of-service (DoS) vulnerability due to a stack buffer overflow in the http_gdpr_decrypt function of the Mercusys MB115-4G device's web interface. An unauthenticated attacker could exploit this vulnerability by sending a specially crafted request to the /cgi/login endpoint, causing memory corruption and the httpd process to crash, resulting in a denial of service for the web administration service.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-12495?


## How do I fix CVE-2026-12495?

No fix has been published for CVE-2026-12495 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-12495 being exploited?

There is no known exploitation of CVE-2026-12495 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12495 and fix it if it is affected.

What it is: CVE-2026-12495 is a medium-severity memory corruption vulnerability in Mercusys MB115-4G, published on 27 Jul 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-2026-12495 in the wild and no public exploit code.

Affected product: Mercusys MB115-4G. 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-2026-12495/ (Markdown: https://insights.sbomify.com/CVE-2026-12495/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12495
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12495
- OSV: https://osv.dev/vulnerability/CVE-2026-12495

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-12495/
Summaries are generated and may contain mistakes; the official description above is the record.