---
id: CVE-2026-77939
title: >-
  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
  Expressi…
summary: >-
  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
  Expressi…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-94
  - CWE-1336
published: '2026-08-28'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T20:23:49.880'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-77939'
references:
  - url: 'https://github.com/flextype/flextype/issues/595'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/flextype-cms-dev-rce-via-post-api-v1-query-endpoint
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.0061
epssPercentile: 0.46968
ingestedAt: '2026-09-08T21:11:12.287Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.