CVE-2026-27210: Pannellum is a lightweight, free, and open source panorama viewer for the web. In versions 3.5.0 through 2.5.6, the hot spot attributes configuration ...

Description

Pannellum is a lightweight, free, and open source panorama viewer for the web. In versions 3.5.0 through 2.5.6, the hot spot attributes configuration property allowed any attribute to be set, including HTML event handler attributes, allowing for potential XSS attacks. This affects websites hosting the standalone viewer HTML file and any other use of untrusted JSON config files (bypassing the protections of the escapeHTML parameter). As certain events fire without any additional user interaction, visiting a standalone viewer URL that points to a malicious config file — without additional user interaction — is sufficient to trigger the vulnerability and execute arbitrary JavaScript code, which can, for example, replace the contents of the page with arbitrary content and make it appear to be hosted by the website hosting the standalone viewer HTML file. This issue has been fixed in version 2.5.7. To workaround, setting the Content-Security-Policy header to script-src-attr 'none' will block execution of inline event handlers, mitigating this vulnerability. Don't host pannellum.htm on a domain that shares cookies with user authentication to mitigate XSS risk.

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS 4.0

5.3/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.32%

23.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Pannellum	Pannellum	>= 2.5.0, < 2.5.7

References

https://github.com/mpetroff/pannellum/commit/9391ef8da6a6a98c6a9f8c97f101adb900523681Patch
https://github.com/mpetroff/pannellum/security/advisories/GHSA-8423-w5wx-h2r6Mitigation, Vendor Advisory

Timeline

Published: Feb 21, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-27210?

Pannellum is a lightweight, free, and open source panorama viewer for the web. In versions 3.5.0 through 2.5.6, the hot spot attributes configuration property allowed any attribute to be set, including HTML event handler attributes, allowing for potential XSS attacks. This affects websites hosting the standalone viewer HTML file and any other use of untrusted JSON config files (bypassing the protections of the escapeHTML parameter). As certain events fire without any additional user interaction, visiting a standalone viewer URL that points to a malicious config file — without additional user interaction — is sufficient to trigger the vulnerability and execute arbitrary JavaScript code, which can, for example, replace the contents of the page with arbitrary content and make it appear to be hosted by the website hosting the standalone viewer HTML file. This issue has been fixed in version 2.5.7. To workaround, setting the Content-Security-Policy header to script-src-attr 'none' will block execution of inline event handlers, mitigating this vulnerability. Don't host pannellum.htm on a domain that shares cookies with user authentication to mitigate XSS risk.

How severe is CVE-2026-27210?

CVE-2026-27210 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.32% probability of exploitation in the next 30 days.

How do I fix CVE-2026-27210?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.