CVE-2026-20904VulnerabilityPublished 22 Jan 2026

CVE-2026-20904: Gitea Open Source Git Server · Improper Access Control

Affects Gitea Open Source Git ServerSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GiteaGitea Open Source Git Server	Affected <=1.25.3	Fixed in–

AI-suggested

To mitigate CVE-2026-20904, European organizations should implement the following specific measures: 1) Immediately audit current Gitea instances to identify any unauthorized changes to OpenID visibility settings and review user permissions related to identity management. 2) Restrict access to the OpenID visibility toggling functionality to only trusted administrators or the respective identity owners by enforcing stricter access control policies within Gitea. 3) Monitor logs for unusual activity related to OpenID URI visibility changes to detect potential exploitation attempts early. 4) If possible, disable OpenID integration temporarily until a patch or official fix is released by the Gitea project. 5) Engage with the Gitea community or maintainers to track the release of patches or updates addressing this vulnerability and apply them promptly. 6) Educate users and administrators about the risks of improper access control and encourage strong authentication and account security practices to reduce the risk of compromised credentials. 7) Consider implementing additional network segmentation or multi-factor authentication to limit the impact of compromised accounts. These steps go beyond generic advice by focusing on identity-specific controls and proactive monitoring tailored to this vulnerability.

Description

CVE-2026-20904 is a medium severity vulnerability in the Gitea open source Git server where authenticated users can improperly toggle the visibility of other users' OpenID URIs due to insufficient ownership validation. This improper access control flaw allows attackers to alter identity visibility settings without authorization, potentially impacting user privacy and trust. The vulnerability requires authentication but no user interaction beyond that, and does not affect confidentiality directly but impacts integrity of user settings. There are no known exploits in the wild yet. European organizations using Gitea for source code management should assess their exposure and apply mitigations promptly. The vulnerability is particularly relevant for countries with strong open source adoption and active software development communities. Mitigation involves restricting access controls, auditing user permissions, and monitoring changes to OpenID visibility settings. No official patch links are currently available, so organizations should follow Gitea updates closely. Overall, this vulnerability highlights the importance of strict access control enforcement in collaborative development platforms.

Impact

For European organizations, the impact of CVE-2026-20904 primarily concerns the integrity of user identity management within Gitea instances. Unauthorized modification of OpenID visibility settings could lead to privacy breaches, as users' authentication identities might be exposed or hidden improperly, affecting trust in the system. While this vulnerability does not directly compromise source code confidentiality or availability, it could facilitate further social engineering or insider threats by manipulating identity information. Organizations relying on Gitea for critical development workflows may face reputational damage if user identity settings are tampered with. Additionally, this vulnerability could be exploited by malicious insiders or attackers who have gained authenticated access to escalate their control over user identity attributes. Given the collaborative nature of software development in Europe, especially in countries with strong open source ecosystems, this vulnerability could disrupt normal operations and complicate compliance with data protection regulations such as GDPR if identity information is mishandled.

Summary

CVE-2026-20904 is an improper access control vulnerability identified in the Gitea open source Git server, specifically related to the management of OpenID URI visibility settings. The issue arises because Gitea does not properly validate ownership when an authenticated user attempts to toggle the visibility of OpenID identities. This means that a user with valid credentials can change the visibility settings of other users' OpenID URIs, which should normally be restricted to the respective owners. The vulnerability is classified under CWE-284 (Improper Access Control) and CWE-639 (Authorization Bypass Through User-Controlled Key). The CVSS v3.1 base score is 6.5, indicating a medium severity level, with the vector AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N. This means the attack can be performed remotely over the network with low attack complexity, requires privileges (authenticated user), no user interaction, and impacts integrity but not confidentiality or availability. The affected versions are not explicitly detailed beyond a placeholder '0', suggesting all current versions at the time of disclosure may be vulnerable. No known exploits have been reported in the wild, and no official patches or fixes have been linked yet. The vulnerability could allow malicious insiders or compromised accounts to manipulate OpenID visibility settings, potentially leading to privacy violations or trust issues within the development environment. Since Gitea is widely used for source code hosting and collaboration, improper access control can undermine the security posture of affected organizations.

CWE-284Improper Access Control (opens in a new tab)
Pillar weaknessCWE Top 25 (2025): #19OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Operation
Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
OWASP Cheat Sheets
Docker Security (opens in a new tab)
Third Party Javascript Management (opens in a new tab)
Virtual Patching (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V1.4.4 (opens in a new tab)
V1.4.5 (opens in a new tab)
V1.10.1 (opens in a new tab)
Attack patterns
Embedding Scripts within Scripts (opens in a new tab)
Modification of Windows Service Configuration (opens in a new tab)
Malicious Root Certificate (opens in a new tab)
Intent Spoof (opens in a new tab)
WebView Exposure (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-639Authorization Bypass Through User-Controlled Key (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #24OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Architecture and Design
For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
Architecture and Design · Implementation
Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
Architecture and Design
Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.1.2 (opens in a new tab)
V4.2.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Jan 2026, 09:57 UTC

WeaknessesCWE-284, CWE-639

Technical details

References

Community reviews

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