Out-of-bounds read in Mongoose - CVE-2026-73261
Published: August 12, 2026
Vulnerability identifier: #VU142184
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-73261
CWE-ID: CWE-125
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to an out-of-bounds read in handle_opt() in src/net_builtin.c when processing crafted TCP options during connection establishment. A remote attacker can send a specially crafted TCP SYN or SYN-ACK packet to cause a denial of service.
Only configurations with MG_ENABLE_TCPIP=1 and TCP usage are vulnerable. The issue can affect both inbound server connections and outbound client connections to an attacker-controlled peer. The connection remains established at the TCP level while application data may be silently reduced or blocked.
Affected software
Mongoose
How to mitigate CVE-2026-73261
Install security update from vendor's website.
Mongoose - update to 7.23