CVE-2026-77939
MEDIUMCVE-2026-77939 is a medium-severity (CVSS 6.5) Code Injection vulnerability. O3 Security confirms whether CVE-2026-77939 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
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…
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-77939.
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.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-77939 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-77939 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-77939. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-77939 in your dependencies?
O3 detects CVE-2026-77939 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.