CVE-2021-22540: XSS in Dart SDK

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-04-22 · updated 2026-06-17
Weakness: CWE-79

Description

Bad validation logic in the Dart SDK versions prior to 2.12.3 allow an attacker to use an XSS attack via DOM clobbering. The validation logic in dart:html for creating DOM nodes from text did not sanitize properly when it came across template tags.

Affected products

Google LLC Dart SDK: before 2.12.3 — fixed in 2.12.3

How to fix

Upgrade to a fixed version: Google LLC Dart SDK 2.12.3. Check the vendor advisory for mitigations.

References

https://github.com/dart-lang/sdk/commit/ce5a1c2392debce967415d4c09359ff2555e3588
https://github.com/dart-lang/sdk/security/advisories/GHSA-3rfv-4jvg-9522
https://github.com/dart-lang/sdk/commit/ce5a1c2392debce967415d4c09359ff2555e3588
https://github.com/dart-lang/sdk/security/advisories/GHSA-3rfv-4jvg-9522

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