Vulnerability · Published Nov 3, 2026 · Assigned by VulnCheck

CVE-2026-121627buku 5.0 through 5.1.1 Stored XSS via bukuserver Bookmark List URL

Medium 6.1

In plain English

A medium-severity cross-site scripting in buku from jarun. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities).

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.2%top 90.9% of all CVEs

Exploited in the wildNo reportsnot in CISA KEV

Attack toolingNoneno public tooling known

Official description

buku 5.0 through 5.1.1 contains a stored cross-site scripting vulnerability in the bukuserver bookmark list that allows attackers to execute script via an unescaped bookmark URL in BookmarkModelView._list_entry(). Attackers can submit a URL containing a double quote and event handler through the unauthenticated /api/bookmarks endpoint to issue same-origin API requests with viewers' credentials.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Ubuntu:22.04:LTS	buku	no fix listed	UBUNTU-CVE-2026-121627
Ubuntu:24.04:LTS	buku	no fix listed	UBUNTU-CVE-2026-121627
Ubuntu:26.04:LTS	buku	no fix listed	UBUNTU-CVE-2026-121627
Ubuntu:26.10	buku	no fix listed	UBUNTU-CVE-2026-121627

Affected products (as reported)

Vendor	Product	Versions
jarun	buku	5.0 – through 5.1.1

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

GitHub Issue #911 issue-tracking
https://github.com/jarun/buku/blob/v5.1.1/bukuserver/views.py#L133 technical-description
https://github.com/jarun/buku product
VulnCheck Advisory: buku 5.0 through 5.1.1 Stored XSS via bukuserver Bookmark List URL third-party-advisory