CVE-2023-1973 — undertow
HIGHCVE-2023-1973 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in undertow. A fix is available for undertow — see the affected versions and patch details below.
Undertow Denial of Service vulnerability
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-2023-1973.
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-2023-1973 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
undertowReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Debian:13 packages — download data is not available via public APIs for these ecosystems.
Description
A flaw was found in Undertow package. Using the FormAuthenticationMechanism, a malicious user could trigger a Denial of Service by sending crafted requests, leading the server to an OutofMemory error, exhausting the server's memory.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦Debian:13 | undertow | all versions | 2.3.18-1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undertow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update undertow to 2.3.18-1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-1973 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-2023-1973 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-1973. 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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat JBoss Enterprise Application Platform | io.undertow/undertow-core:2.2.30.SP1-redhat-00001 | RHSA-2024:1677 |
| Red Hat JBoss Enterprise Application Platform 7.1 EUS for RHEL 7 | eap7-activemq-artemis-0:1.5.5.016-1.redhat_00001.1.ep7.el7 | RHSA-2025:4226 |
| Red Hat JBoss Enterprise Application Platform 7.3 EUS for RHEL 7 | eap7-jackson-annotations-0:2.10.4-3.redhat_00006.1.el7eap | RHSA-2025:9583 |
| Red Hat JBoss Enterprise Application Platform 7.4 for RHEL 8 | eap7-undertow-0:2.2.30-1.SP1_redhat_00001.1.el8eap | RHSA-2024:1675 |
| Red Hat JBoss Enterprise Application Platform 7.4 for RHEL 9 | eap7-undertow-0:2.2.30-1.SP1_redhat_00001.1.el9eap | RHSA-2024:1676 |
| Red Hat JBoss Enterprise Application Platform 7.4 on RHEL 7 | eap7-undertow-0:2.2.30-1.SP1_redhat_00001.1.el7eap | RHSA-2024:1674 |
| Red Hat JBoss Enterprise Application Platform 8 | undertow-core | RHSA-2024:2763 |
| Red Hat JBoss Enterprise Application Platform 8.0 for RHEL 8 | eap8-undertow-0:2.3.11-1.SP1_redhat_00001.1.el8eap | RHSA-2024:2764 |
Frequently Asked Questions
Is CVE-2023-1973 in your dependencies?
O3 Security finds CVE-2023-1973 across Debian:13 dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.