CVE-2026-77939 Flextype CMS 1.0.0-dev RCE via POST /api/v1/query Endpoint
Authenticated attackers can inject expressions to read arbitrary files and potentially execute code via the query endpoint.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-77939?
CVE-2026-77939 is a high-severity code injection vulnerability in flextype, published on 28 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Flextype CMS through v1.0.0-dev contains an expression language injection vulnerability that allows authenticated attackers with a valid API token to read arbitrary files by passing unsanitized user-supplied input to the Symfony ExpressionLanguage engine via the POST /api/v1/query endpoint. Attackers can leverage exposed application objects including filesystem() and serializers() within the evaluation scope to read arbitrary server files and achieve conditional remote code execution if a PHP file can be placed on disk through a secondary vector.
Which versions are affected by CVE-2026-77939?
How do I fix CVE-2026-77939?
No fix has been published for CVE-2026-77939 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-2026-77939 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77939 exists.
Sources
Also known as GHSA-j8rr-2wmh-q2h8.