# CVE-2026-101039: FAST FAC1900R devdiscover Service copy_msg_element stack-based overflow

> Remote attackers can exploit a stack-based buffer overflow in the devdiscover service to execute arbitrary code on FAST FAC1900R devices.

- **Severity:** Critical 10.0 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** GHSA-6x6g-w7q4-663p

## What is CVE-2026-101039?

CVE-2026-101039 is a critical memory corruption vulnerability in FAST FAC1900R, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was identified in FAST FAC1900R 20190827_2.0.2. Affected by this issue is the function copy_msg_element of the component devdiscover Service. Such manipulation leads to stack-based buffer overflow. The attack can be executed remotely. The exploit is publicly available and might be used. The vendor was contacted early about this disclosure but did not respond in any way.

Weakness: CWE-121 (Stack-based Buffer Overflow), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-101039?


## How do I fix CVE-2026-101039?

No fix has been published for CVE-2026-101039 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-101039 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101039 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-101039 and fix it if it is affected.

What it is: CVE-2026-101039 is a critical memory corruption vulnerability in FAST FAC1900R, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-101039 exists.

Affected product: FAST FAC1900R. 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-2026-101039/ (Markdown: https://insights.sbomify.com/CVE-2026-101039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-101039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-101039
- OSV: https://osv.dev/vulnerability/CVE-2026-101039

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-101039/
Summaries are generated and may contain mistakes; the official description above is the record.