CVE-2026-21889
Published: 14 January 2026
Summary
CVE-2026-21889 is a high-severity Improper Access Control (CWE-284) vulnerability in Weblate Weblate. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 14.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
The access control policy and procedures directly mandate and enforce proper access control mechanisms across the organization.
Device lock enforces restricted access until re-authentication, directly reducing unauthorized use of active sessions.
Supervision and review of access control activities directly detects and remediates improper access configurations or usages.
Explicitly identifying and documenting actions permitted without identification or authentication enforces proper access control boundaries by defining justified exceptions.
By automatically labeling outputs with security attributes, the control supports attribute-based enforcement and reduces exploitability of improper access control weaknesses.
Associating and retaining security attributes with data directly supports enforcement of access control decisions across storage, processing, and transmission.
Requiring prior authorization for each remote access type prevents improper access control over remote connections.
Requiring authorization of wireless access before allowing connections enforces proper access control for this access method.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Improper access control in public-facing Weblate web app directly enables remote unauthenticated file access via T1190.
NVD Description
Weblate is a web based localization tool. Prior to 5.15.2, the screenshot images were served directly by the HTTP server without proper access control. This could allow an unauthenticated user to access screenshots after guessing their filename. This vulnerability is…
more
fixed in 5.15.2.
Deeper analysisAI
CVE-2026-21889 is an improper access control vulnerability in Weblate, a web-based localization tool. In versions prior to 5.15.2, screenshot images were served directly by the HTTP server without adequate access restrictions, enabling unauthorized access upon filename guessing. The issue is classified under CWE-284 and carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), reflecting high confidentiality impact with no effects on integrity or availability.
An unauthenticated attacker can exploit this vulnerability remotely with low complexity and no user interaction required. By guessing the filenames of screenshot images, the attacker gains unauthorized access to potentially sensitive localization-related images, such as those containing interface previews or other project-specific visuals stored by Weblate instances.
The vulnerability is addressed in Weblate version 5.15.2, where access controls were implemented to prevent direct serving of these files. Official mitigation details are available in the Weblate security advisory (GHSA-3g2f-4rjg-9385), along with the fixing pull request (#17516) and commit (a6eb5fd0299780eca286be8ff187dc2d10feec47), recommending immediate upgrades for affected deployments.
Details
- CWE(s)