vBulletin - RCE (CVE-2026-61511)

CVE-2026-61511 is a critical eval injection vulnerability in vBulletin that allows unauthenticated remote attackers to execute arbitrary PHP code through the unauthenticated template-rendering route. Exploitation involves crafted input in the pagenav[pagenumber] parameter to bypass filtering and compromise the confidentiality, integrity, and availability of the affected server.

CrowdSec has been tracking this vulnerability and its exploits since 28th of July 2026.

CrowdSec network observations suggest that most exploitation of CVE-2026-61511 involves focused reconnaissance to identify viable targets. Attackers typically tailor their campaigns based on system exposure and configuration. It is unlikely that a given attack is accidental. Additionally, according to week-over-week analysis by CrowdSec, exploitation of CVE-2026-61511 is surging. Attack volumes are spiking well above historical norms, indicating widespread and escalating interest from threat actors. CVE-2026-61511 is currently experiencing high visibility and active exploitation across the internet.

Attackers target various endpoints with a URL-encoded POST parameter routestring=ajax%2Frender%2Fpagenav and a crafted pagenav[pagenumber] expression designed to trigger eval injection in vBulletin’s template runtime. Detection should focus on requests containing the ajax/render/pagenav route and deeply nested arithmetic, concatenation, or exponentiation syntax in the pagenav[pagenumber] parameter.