CVE-2026-50279
Fix: craftcms/cms@9cc493bCVE-2026-50279 is a CWE-285 vulnerability in craftcms/cms. O3 Security confirms whether CVE-2026-50279 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Craft CMS: Authorship spoofing in `entries/save-entry` via pre-check/post-mutation authorization gap
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.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-50279.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
craftcms/cmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Craft CMS is a content management system (CMS). IN versions 5.0.0-RC1 and above prior to 5.9.21, theEntriesController::actionSaveEntry() performs entry-edit permission checks before request-controlled author changes are applied to the model, allowing for authorship spoofing. The subsequent author mutation path accepts attacker-supplied authors / author parameters and allows the change when the current user is one of the old authors. Because the controller does not re-run authorization after mutating the author list, a low-privileged user can reassign an entry’s authorship to another user without holding the dedicated peer-author-change permission. This issue has been fixed in version 5.9.21.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | craftcms/cms | ≥ 5.0.0-RC1&&< 5.9.21 | 5.9.21 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for craftcms/cms. 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.
Fix
Update craftcms/cms to 5.9.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50279 is resolved across your whole dependency graph.
Workarounds
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-2026-50279 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-2026-50279. 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-2026-50279 in your dependencies?
O3 detects CVE-2026-50279 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.