XSS in Cal.com Self-Hosted (Cal.diy)
CVE-2026-57858
Cal.com Cal.diy versions 2.1.1 through 6.2.0 contain a stored cross-site scripting vulnerability in the BookingPageTagManager component that allows authenticated event owners to inject arbitrary JavaScript by supplying a malicious analytics tracking ID without sanitization. Attackers can close the inline script string literal with a crafted payload that executes in the browser of every visitor to the affected public booking page, enabling session cookie theft, forged authenticated requests, and wormable propagation by chaining with CSRF-able endpoints to persist payloads on additional events.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.9 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L.
EPSS exploit prediction
EPSS: 0.004 (28.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 28th percentile — 28.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Cal.com Self-Hosted (Cal.diy) — versions 2.1.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/calcom/cal.com (product)
- ashtonr.com/blog/cve-2026-57858/ (technical-description)
- www.vulncheck.com/advisories/cal-com-cal-diy-stored-xss-via-bookingpagetagmanag… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-57858?
- CVE-2026-57858 is a high-severity vulnerability in Cal.com Self-Hosted (Cal.diy), classified under Cross-site Scripting. CVSS score: 8.9/10. Published 2026-08-12.
- How severe is CVE-2026-57858?
- High severity. CVSS v3 base score is 8.9 out of 10.
- Is CVE-2026-57858 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.