CVE-2026-57886 in Gitea
Summary
by MITRE • 08/13/2026
Cross-repository issue/comment attachment re-linking can expose private attachment content
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/13/2026
This vulnerability involves a cross-repository issue comment attachment re-linking mechanism that can inadvertently expose private attachment content to unauthorized users. The flaw occurs when attachments from one repository are referenced or re-linked in comments within a different repository, potentially bypassing access controls that should restrict content visibility. When users interact with these re-linked attachments through comment threads, the system fails to properly validate whether the requesting user has appropriate permissions to access the original attachment content.
The technical implementation of this vulnerability stems from insufficient access control validation during cross-repository reference resolution. When an attachment is referenced in a comment across repository boundaries, the system should verify that the user has proper authorization to view both the comment context and the underlying attachment. However, the current mechanism only validates access to the comment thread itself while neglecting to re-authenticate access to the original attachment data. This creates a scenario where users with read access to a public or shared repository comment thread can potentially access private attachments that were originally stored in a separate restricted repository.
The operational impact of this vulnerability extends beyond simple information disclosure, as it represents a privilege escalation vector that can lead to unauthorized data exposure. Attackers could exploit this weakness by creating malicious comment threads that reference private attachments from other repositories, effectively circumventing repository-level access controls. This vulnerability particularly affects collaborative platforms where users may have varying permission levels across multiple repositories, and the system's trust model assumes that valid references automatically grant access without additional validation.
Security implications of this flaw align with CWE-284 Access Control Issues, specifically addressing inadequate access control mechanisms in cross-domain or cross-repository contexts. The vulnerability also maps to ATT&CK technique T1078 Valid Accounts, as it exploits legitimate user permissions to access unauthorized data through reference manipulation rather than direct privilege escalation. Organizations using platforms with this vulnerability face potential compliance violations if private intellectual property, sensitive documentation, or confidential attachments are exposed to unauthorized parties.
Mitigation strategies should focus on implementing strict access control validation at every reference point during cross-repository attachment resolution. Systems must perform independent permission checks for both the comment context and the original attachment before rendering any content. Additionally, implementing proper audit logging of attachment access patterns can help detect anomalous behavior indicating potential exploitation attempts. Regular security reviews of cross-repository functionality and mandatory access control validation for all inter-repository references should be enforced to prevent similar issues in future implementations.