CVE-2026-21889
Published: 14 January 2026
Summary
CVE-2026-21889 is a low-severity Improper Access Control (CWE-284) vulnerability in Weblate Weblate. Its CVSS base score is 2.3 (Low).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 16.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 AC-3 (Access Enforcement) and SC-14 (Public Access Protections).
Deeper analysis
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.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2452
Vulnerability details
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…
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fixed in 5.15.2.
- CWE(s)
Related Threats
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.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
AC-3 enforces approved authorizations for access to system resources like screenshot files, directly preventing unauthorized access via HTTP server without proper controls.
SC-14 controls access to publicly accessible system components such as the web server, mitigating unauthenticated exposure of screenshots through filename guessing.
AC-22 designates and authorizes content for public accessibility, reducing the risk of sensitive screenshots being served without restrictions.