CVE-2026-19874 Konami's Metal Gear Online 3 contains a heap-based buffer overflow
An attacker can achieve arbitrary code execution in Metal Gear Online 3 by exploiting a heap-based buffer overflow via oversized lobby data fields.
- 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-2026-19874?
CVE-2026-19874 is a critical memory corruption vulnerability in Konami Metal Gear Online 3, published on 24 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A heap-based buffer overflow vulnerability exists in Konami's Metal Gear Online 3, originating from improper validation of lobby data fields related to kicked players. The affected function processes a list of kicked player identifiers using the lobby data key "kick_num" to determine the number of entries, and individual kicked player IDs supplied via keys in the format "kicked_id_%i". The function does not validate that "kick_num" falls within the expected bounds. The game design limits matches to a maximum of 16 players, and the corresponding buffer for storing kicked player IDs is sized accordingly. If "kick_num" exceeds this limit, the function continues writing the provided player IDs past the end of the intended buffer and into adjacent memory regions. These adjacent regions contain Steam callback handler structures responsible for processing lobby data updates, lobby messages, and other related events. By supplying an oversized "kick_num" value and appropriate "kicked_id_%i" fields, an attacker can overwrite fields within the callback handler structures, including function pointers and callback argument values. Successful exploitation may enable control-flow hijacking, potentially allowing arbitrary code execution within the game process.
Weakness: CWE-122
Which versions are affected by CVE-2026-19874?
How do I fix CVE-2026-19874?
No fix has been published for CVE-2026-19874 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-2026-19874 being exploited?
There is no known exploitation of CVE-2026-19874 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-ggf5-p56j-ccc2.