CVE-2023-1973 – This vulnerability in Undertow's FormAuthentica... (How to Fix)

Q: What is the severity of CVE-2023-1973?

CVE-2023-1973 has a CVSS score of 7.5 (HIGH). This vulnerability in Undertow's FormAuthenticationMechanism allows attackers to cause denial of service by sending specially crafted requests that trigger out-of-memory errors. It affects systems using Undertow with form authentication enabled. The flaw can exhaust server memory, making services unavailable.

📋 TL;DR

This vulnerability in Undertow's FormAuthenticationMechanism allows attackers to cause denial of service by sending specially crafted requests that trigger out-of-memory errors. It affects systems using Undertow with form authentication enabled. The flaw can exhaust server memory, making services unavailable.

💻 Affected Systems

Products:

Undertow
Red Hat JBoss EAP
Red Hat JBoss Web Server
Red Hat Single Sign-On

Versions: Undertow versions before 2.3.10.Final and related Red Hat products as specified in advisories

Operating Systems: Linux, Windows, All platforms running affected Undertow versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires FormAuthenticationMechanism to be enabled and accessible.

⚠️ Manual Verification Required

This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.

Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).

🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.

Recommended Actions:

Review the CVE details at NVD
Check vendor security advisories for your specific version
Test if the vulnerability is exploitable in your environment
Consider updating to the latest version as a precaution

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete server unavailability due to memory exhaustion, requiring restart and potentially causing extended downtime.

🟠

Likely Case

Service disruption affecting availability of web applications using form authentication.

🟢

If Mitigated

Minimal impact with proper memory limits and monitoring in place.

🌐 Internet-Facing: HIGH - Internet-facing servers with form authentication are directly exposed to crafted requests.

🏢 Internal Only: MEDIUM - Internal systems could still be targeted by authenticated users or compromised internal accounts.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Crafted requests can be sent without authentication to vulnerable endpoints.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Undertow 2.3.10.Final or later, and corresponding Red Hat product updates

Vendor Advisory: https://access.redhat.com/errata/RHSA-2024:1674

Restart Required: Yes

Instructions:

1. Identify affected Undertow or Red Hat product installations. 2. Apply vendor-provided patches. 3. Restart affected services. 4. Verify patch application.

🔧 Temporary Workarounds

Disable Form Authentication

all

Temporarily disable FormAuthenticationMechanism if not required

Modify undertow subsystem configuration to use alternative authentication mechanisms

Implement Request Limits

all

Configure request size limits and connection throttling

Set max-post-size and other request limits in Undertow configuration

🧯 If You Can't Patch

Implement WAF rules to block suspicious form authentication requests
Monitor memory usage and set up alerts for abnormal patterns

🔍 How to Verify

Check if Vulnerable:

Check Undertow version and verify if FormAuthenticationMechanism is enabled in configuration

Check Version:

java -jar undertow-core.jar --version or check application server version

Verify Fix Applied:

Confirm Undertow version is 2.3.10.Final or later, or corresponding Red Hat product patch level

📡 Detection & Monitoring

Log Indicators:

OutOfMemoryError in logs
Abnormally high memory usage patterns
Multiple failed authentication attempts

Network Indicators:

Unusually large POST requests to authentication endpoints
High volume of requests to form login pages

SIEM Query:

source="application.logs" AND ("OutOfMemoryError" OR "java.lang.OutOfMemoryError") AND "undertow"

📊 Metadata

CVE ID: CVE-2023-1973

CVSS v3 Score: 7.5 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-20

Published: November 7, 2024

Last Updated: November 8, 2024

🔗 References

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