CVE-2025-10990 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in rexml. A fix is available for rexml — see the affected versions and patch details below.
Rexml: rexml: denial of service via inefficient regex parsing
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2025-10990.
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-2025-10990 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 379,145 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
rexmlReal-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
Impact
The REXML gem before 3.3.9 has a ReDoS vulnerability when it parses an XML that has many digits between &# and x...; in a hex numeric character reference (&#x...;).
This does not happen with Ruby 3.2 or later. Ruby 3.1 is the only affected maintained Ruby. Note that Ruby 3.1 will reach EOL on 2025-03.
Patches
The REXML gem 3.3.9 or later include the patch to fix the vulnerability.
Workarounds
Use Ruby 3.2 or later instead of Ruby 3.1.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rexml | all versions | 3.3.9bundle update rexml --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rexml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update rexml to 3.3.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-10990 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-2025-10990 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-10990. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is rated as a moderate severity because it allows attackers to exploit inefficient regex parsing in hex numeric character references (&#x...;), causing a ReDoS and impacting availability, it requires specific malicious input but does not affect confidentiality or integrity. Satellite employs…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Satellite 6.16 for RHEL 8 | puppet-agent-0:8.8.1-3.el8sat | RHSA-2025:17613 |
| Red Hat Satellite 6.17 for RHEL 9 | puppet-agent-0:8.8.1-3.el9sat | RHSA-2025:17606 |
| Satellite Client 6 for RHEL 8 | puppet-agent-0:7.34.0-4.el8sat | RHSA-2025:17693 |
Frequently Asked Questions
Is CVE-2025-10990 in your dependencies?
O3 Security finds CVE-2025-10990 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.