CVE-2026-110101: Koillection through 1.8.4 Stored XSS via Datum File Attachment Uploads

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-13 · updated 2026-10-16
Weakness: CWE-79

Description

Koillection through 1.8.4 contains a stored cross-site scripting vulnerability that allows authenticated users to upload HTML files as Datum file attachments lacking MIME restrictions. Attackers can upload HTML payloads via POST /api/data/{id}/file, served as text/html from public/uploads, executing JavaScript in victims' sessions to perform actions on their behalf.

Affected products

benjaminjonard Koillection: through 1.8.4

References

https://github.com/benjaminjonard/koillection/blob/1.8.4/src/Entity/Datum.php#L141-L145
https://github.com/benjaminjonard/koillection/blob/1.8.4/src/Service/ImageHandler.php#L43-L50
https://github.com/benjaminjonard/koillection/issues/1609
https://github.com/benjaminjonard/koillection/releases/tag/1.8.4
https://www.vulncheck.com/advisories/koillection-through-1.8.4-stored-xss-via-datum-file-attachment-uploads
https://github.com/benjaminjonard/koillection/issues/1609

Get alerted when CVE-2026-110101 or the next vulnerability affects your stack