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The vulnerability operates as a side-channel information disclosure flaw within the `/api/v1/user` endpoint’s authentication logic. When an unauthenticated or incorrectly authenticated request is made to this API endpoint, the application’s internal processing flow differs based on whether the submitted username parameter corresponds to a valid, existing user account in the database. This discrepancy manifests in subtle differences in the HTTP response, such as marginally different server processing times or distinct error message structures before a generic failure is returned. An attacker can systematically probe this endpoint with a list of potential usernames. By analyzing the timing or the nuanced content of the authentication failure responses, the attacker can infer which usernames are registered within the Gitea instance. This user enumeration bypasses the intended security design where authentication failures should be indistinguishable, thereby facilitating targeted credential stuffing or social engineering attacks by confirming valid account identifiers.
Platform: Gitea
Version: < 1.25.2
Vulnerability: User Enumeration
Severity: Moderate
date: 2026-01-02
Prediction: 2026-01-09 Patch
What Undercode Say:
!/bin/bash
Probing the endpoint for timing differentials
for user in candidate1 candidate2 admin; do
time curl -s -o /dev/null -w “%{http_code}” “https://target.gitea.instance/api/v1/user?username=$user”
echo ” – $user”
done
Example raw API request
curl -X GET “http://localhost:3000/api/v1/user” \
-H “accept: application/json” \
-H “Authorization: token INVALID_OR_EMPTY”
How Exploit:
Automated scripts send sequential API requests with common usernames, measuring response times or parsing slight variations in error JSON to identify valid users.
Protection from this CVE
Upgrade to Gitea version 1.25.2 or later, which standardizes the endpoint’s response behavior for all failed authentication attempts, eliminating the discernible difference.
Impact:
Information Disclosure, leading to User Account Enumeration, increasing risk of subsequent targeted attacks.
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Sources:
Reported By: github.com
Extra Source Hub:
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