RCE in Flextype
CVE-2026-77939
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.
Vulnerability class: RCE (Remote Code Execution)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.006 (47.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 48th percentile — 47.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/flextype/flextype/issues/595 (issue-tracking, technical-description, exploit)
- www.vulncheck.com/advisories/flextype-cms-dev-rce-via-post-api-v1-query-endpoint (third-party-advisory)
Frequently asked questions
- What is CVE-2026-77939?
- CVE-2026-77939 is a medium-severity vulnerability in Flextype, classified under Code Injection. CVSS score: 6.5/10. Published 2026-08-28.
- How severe is CVE-2026-77939?
- Medium severity. CVSS v3 base score is 6.5 out of 10.