CVE-2026-48821

CVE-2026-48821 is a medium-severity vulnerability with a CVSS 3.x base score of 5.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Description

Shaarli is a personal bookmarking service. Versions 0.16.1 and prior contain a DOM-based Cross-Site Scripting (XSS) vulnerability in the Thumbnail Synchronizer feature. When an administrator runs the thumbnail update process, malicious bookmark titles are returned via an AJAX response and inserted into the DOM using innerHTML without proper sanitization. The issue originates from the interaction between the backend thumbnail update endpoint and the frontend JavaScript responsible for rendering update progress. On the backend, the ThumbnailsController::ajaxUpdate method returns bookmark data formatted using the 'raw' formatter. This includes the unescaped bookmark title in the JSON response. On the client side, the script thumbnails-update.js processes this AJAX response and dynamically updates the progress interface. Administrators using the thumbnail synchronization feature are affected and exploitation could lead to session hijacking, privilege escalation, backdoor injection and full compromise. This issue has been fixed in version 0.16.2.

Frequently asked questions

What is CVE-2026-48821?
Shaarli is a personal bookmarking service. Versions 0.16.1 and prior contain a DOM-based Cross-Site Scripting (XSS) vulnerability in the Thumbnail Synchronizer feature. When an administrator runs the thumbnail update process, malicious bookmark titles are returned via an AJAX response and inserted into the DOM using innerHTML without proper sanitization. The issue originates from the interaction between the backend thumbnail update endpoint and the frontend JavaScript responsible for rendering update progress. On the backend, the ThumbnailsController::ajaxUpdate method returns bookmark data formatted using the 'raw' formatter. This includes the unescaped bookmark title in the JSON response. On the client side, the script thumbnails-update.js processes this AJAX response and dynamically updates the progress interface. Administrators using the thumbnail synchronization feature are affected and exploitation could lead to session hijacking, privilege escalation, backdoor injection and full compromise. This issue has been fixed in version 0.16.2.
How severe is CVE-2026-48821?
CVE-2026-48821 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over local access with low attack complexity, requires high privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-48821 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-48821?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-48821 have an EU (EUVD) identifier?
Yes. CVE-2026-48821 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-37796.
When was CVE-2026-48821 published?
CVE-2026-48821 was published on 2026-06-17 and last updated on 2026-06-23.

References

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