CVE-2021-26540Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the "allowedIframeHostnames" option…
- 5.3MediumCVSS base score
- 1.8%Exploitation in 30 daysEPSS · top 21% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the "allowedIframeHostnames" option when the "allowIframeRelativeUrls" is set to true, which allows attackers to bypass hostname whitelist for iframe element, related using an src value that starts with "/\\example.com".
Timeline
ID reserved
By mitre
- 7 days later
· 7 days later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Medium5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
- EPSS (exploitation in 30 days)
- 1.8% · top 21% of all CVEs (15 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.
Affected products
n/a
- affected n/a
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- npmsanitize-htmlGHSA-mjxr-4v3x-q3m4 (opens in a new tab)
References
References3
- https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/apostrophecms/sanitize-html/pull/460 (opens in a new tab)x_refsource_MISCx_transferred
- https://advisory.checkmarx.net/advisory/CX-2021-4309 (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-1141 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-mjxr-4v3x-q3m4 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-26540)Record last updated .