CVE-2024-28199 is a high-severity (CVSS 7.1) Cross-site Scripting (XSS) vulnerability in phlex. A fix is available for phlex — see the affected versions and patch details below.
Cross-site Scripting (XSS) possible with maliciously formed HTML attribute names and values in Phlex
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-28199.
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.
How urgent is this, really
CVE-2024-28199 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
phlex💎phlex💎phlex💎phlex💎phlex💎phlex💎phlex💎phlex+2 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
phlex is an open source framework for building object-oriented views in Ruby. There is a potential cross-site scripting (XSS) vulnerability that can be exploited via maliciously crafted user data. This was due to improper case-sensitivity in the code that was meant to prevent these attacks. If you render an <a> tag with an href attribute set to a user-provided link, that link could potentially execute JavaScript when clicked by another user. If you splat user-provided attributes when rendering any HTML tag, malicious event attributes could be included in the output, executing JavaScript when the events are triggered by another user. Patches are available on RubyGems for all 1.x minor versions. Users are advised to upgrade. Users unable to upgrade should consider configuring a content security policy that does not allow unsafe-inline.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | phlex | ≥ 1.9.0&&< 1.9.1 | 1.9.1bundle update phlex --conservative |
| 💎RubyGems | phlex | ≥ 1.8.0&&< 1.8.2 | 1.8.2bundle update phlex --conservative |
| 💎RubyGems | phlex | ≥ 1.7.0&&< 1.7.1 | 1.7.1bundle update phlex --conservative |
| 💎RubyGems | phlex | ≥ 1.6.0&&< 1.6.2 | 1.6.2bundle update phlex --conservative |
| 💎RubyGems | phlex | ≥ 1.5.0&&< 1.5.2 | 1.5.2bundle update phlex --conservative |
| 💎RubyGems | phlex | ≥ 1.4.0&&< 1.4.1 | 1.4.1bundle update phlex --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phlex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update phlex to 1.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-28199 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2024-28199 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-28199. 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-2024-28199 in your dependencies?
O3 Security finds CVE-2024-28199 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.