CVE-2026-85440 MOOS core-moos through 10.4.0 MOOSDB Pre-Authentication Heap Overflow via Negative Packet Length

Critical 9.3 Published 3 Sep 2026 Updated 4 Sep 2026

Remote attackers can achieve arbitrary code execution via a pre-authentication heap overflow in MOOSDB caused by improper handling of negative packet lengths.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-85440?

CVE-2026-85440 is a critical memory corruption vulnerability in themoos core-moos, published on 3 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

MOOS core-moos through 10.4.0 contains a pre-authentication heap overflow vulnerability in MOOSCommPkt packet handling that allows remote attackers to write arbitrary data by declaring a negative packet length. Attackers can exploit the signed integer check in InflateTo() and negative size conversion in recv() to overflow a four-byte heap buffer during the HandShake phase before authentication.

Weakness: CWE-787

Which versions are affected by CVE-2026-85440?

It affects 1 product.

Products include Themoos Core-Moos.

How do I fix CVE-2026-85440?

No fix has been published for CVE-2026-85440 yet. Limit exposure of the affected software until one is available.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2026-85440 being exploited?

There is no known exploitation of CVE-2026-85440 in the wild and no public exploit code.

Sources

Also known as GHSA-m984-rrgf-rcwh.