Vulnerability · Published Sep 3, 2026 · Assigned by VulnCheck

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

Critical 9.8

In plain English

A critical-severity out-of-bounds write in core-moos from themoos. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.0% (higher than 64% of all known vulnerabilities).

Severity (CVSS 3.1)9.8Critical

Exploit odds (30 days)1.0%top 36.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
themoos	core-moos	0 – through 10.4.0

Weakness: CWE-787 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

Pull Request #82 issue-tracking, patch
Proposed fix commit (pull request not merged) patch
https://github.com/themoos/core-moos product
MOOSCommPkt.cpp (verified sink) technical-description
VulnCheck Advisory: MOOS core-moos through 10.4.0 MOOSDB Pre-Authentication Heap Overflow via Negative Packet Length third-party-advisory