CVE-2026-12209 RubyLouvre avalon Template Filter index.js prototype pollution
Remote attackers can exploit prototype pollution in the RubyLouvre avalon template filter to execute arbitrary code or escalate privileges.
- 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-2026-12209?
CVE-2026-12209 is a medium-severity code injection vulnerability in RubyLouvre avalon, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A security vulnerability has been detected in RubyLouvre avalon up to 2.2.10. The impacted element is an unknown function of the file src/filters/index.js of the component Template Filter Handler. Such manipulation leads to improperly controlled modification of object prototype attributes. It is possible to launch the attack remotely. The exploit has been disclosed publicly and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
Which versions are affected by CVE-2026-12209?
How do I fix CVE-2026-12209?
No fix has been published for CVE-2026-12209 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-12209 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-12209 exists.
Sources
Also known as GHSA-785f-3qgq-ghq3.