CVE-2021-39123
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to cause a Denial of Service (DoS) in Atlassian Jira Server and Data Center by exploiting a specific REST endpoint. The attack impacts application availability without requiring authentication. Organizations running affected Jira versions before 8.16.0 are vulnerable.
💻 Affected Systems
- Atlassian Jira Server
- Atlassian Jira Data Center
📦 What is this software?
Data Center by Atlassian
Jira by Atlassian
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption making Jira unavailable to all users, potentially affecting business operations that depend on issue tracking and project management.
Likely Case
Temporary service degradation or intermittent outages affecting user productivity and workflow continuity.
If Mitigated
Minimal impact with proper network controls and monitoring in place to detect and block exploitation attempts.
🎯 Exploit Status
The vulnerability requires no authentication and targets a specific REST endpoint, making exploitation straightforward for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.16.0 and later
Vendor Advisory: https://jira.atlassian.com/browse/JRASERVER-72237
Restart Required: Yes
Instructions:
1. Backup your Jira instance and database. 2. Download Jira version 8.16.0 or later from Atlassian's website. 3. Follow Atlassian's upgrade documentation for your specific deployment type. 4. Restart Jira services after upgrade completion.
🔧 Temporary Workarounds
Block Vulnerable Endpoint
allConfigure web application firewall or reverse proxy to block access to the /rest/gadget/1.0/createdVsResolved/generate endpoint
# Example for Apache mod_rewrite
RewriteRule ^/rest/gadget/1.0/createdVsResolved/generate - [F,L]
# Example for Nginx
location ~ ^/rest/gadget/1.0/createdVsResolved/generate { return 403; }
🧯 If You Can't Patch
- Implement network segmentation to restrict access to Jira from untrusted networks
- Deploy rate limiting on the vulnerable endpoint to prevent DoS attacks
🔍 How to Verify
Check if Vulnerable:
Check Jira version via Admin → System → System Info. If version is below 8.16.0, the system is vulnerable.Check Version:
Check Jira web interface at Admin → System → System Info or run: cat /path/to/jira/atlassian-jira/META-INF/maven/com.atlassian.jira/jira-core/pom.xml | grep versionVerify Fix Applied:
After upgrading, verify version is 8.16.0 or higher and test that the /rest/gadget/1.0/createdVsResolved/generate endpoint no longer causes service disruption.📡 Detection & Monitoring
Log Indicators:
- High frequency of requests to /rest/gadget/1.0/createdVsResolved/generate endpoint
- Increased error rates or timeout messages in Jira logs
- Unusual traffic patterns from single IP addresses
Network Indicators:
- Bursts of HTTP POST/GET requests to the vulnerable endpoint
- Traffic spikes from external sources to Jira REST API
SIEM Query:
source="jira.log" AND (uri_path="/rest/gadget/1.0/createdVsResolved/generate" OR error="timeout") | stats count by src_ip