CVE-2026-118660

Happy DOM: SSRF via iframe and link stylesheet when parsing untrusted HTML

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Prior to 21.0.0, Happy DOM loads iframe src URLs and link rel="stylesheet" href URLs by default while parsing untrusted HTML on the server because disableIframePageLoading and disableCSSFileLoading default to false. An attacker who controls parsed HTML can therefore cause server-side requests to arbitrary internal or cloud endpoints without an application opt-in and may expose confidential responses or credentials returned by those endpoints. This issue is fixed in version 21.0.0.

Affected

capricorn86 · happy-dom

CVSS v3.1 GITHUB

8.6 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

EPSS

0.40% chance of exploitation in the next 30 days, 35th percentile

Published

2026-10-28

Updated

2026-10-29

Proof-of-concept exploits (1)

• advisories/GHSA-c8p4-j97h-3vg8find archive

CVE references

• capricorn86/happy-dom/commit/0a99c7525a1d0043e3182843ae33466ab7b19e74REFERENCE
• capricorn86/happy-dom/pull/2502REFERENCE
• capricorn86/happy-dom/releases/tag/v21.0.0REFERENCE
• capricorn86/happy-dom/security/advisories/GHSA-c8p4-j97h-3vg8REFERENCE

References

• CVE Record
• NVD entry