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Vulnerability record · CVE-2026-66843 · published 6 August 2026

CVE-2026-66843: Rrrene htmlsanitizeex inclusion from untrusted sphere vulnerability

Rrrene · Htmlsanitizeex

Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an <object> element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase "javascript:", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive. This is not unconditional cross-site scripting. A javascript: URL does not execute through <object data> in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path. This issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.

2.3 CVSS 4.0 Low EPSS 0.51% · top 58.7% CWE-829 · Inclusion from untrusted sphere
2.3CVSS 4.0 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
5References
19 Aug 2026Last modified by NVD

Description

Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an <object> element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase "javascript:", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive. This is not unconditional cross-site scripting. A javascript: URL does not execute through <object data> in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path. This issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.

CVSS:4.0/AV:N/AC:L/AT:P/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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cna.erlef.org/cves/CVE-2026-66843.html PatchThird Party Advisory
https://github.com/rrrene/html_sanitize_ex/commit/bec27fec4de99e40c68c4285a610e09e791a3eaf Patch
https://github.com/rrrene/html_sanitize_ex/commit/ce038aa1af5a960d50f8eb5d368cc57bb2b9a9f0
https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-xmm9-jc22-rcgj Broken Link
https://osv.dev/vulnerability/EEF-CVE-2026-66843 PatchThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.2CVE-2026-68749Rrrene htmlsanitizeex inefficient regular expression (redos) vulnerabilityInefficient Regular Expression Complexity vulnerability in the CSS scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to e…EPSS 0.80%8.2CVE-2026-68750Rrrene htmlsanitizeex vulnerabilityInefficient Algorithmic Complexity vulnerability in the traversal engine in rrrene html_sanitize_ex allows an unauthenticated remote attacker to exha…EPSS 0.80%4.8CVE-2026-66370Rrrene htmlsanitizeex open redirect vulnerabilityURL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote a…EPSS 0.40%2.3CVE-2026-68747Rrrene htmlsanitizeex injection vulnerabilityImproper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') vulnerability in the CSS scrubber in rrrene html_s…EPSS 0.45%2.3CVE-2026-66829Rrrene htmlsanitizeex open redirect vulnerabilityURL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to force …EPSS 0.57%9.8CVE-2026-0770Langflow validate endpoint exec_globals remote code executionLangflow mishandles the exec_globals parameter passed to its validate endpoint, allowing functionality from an untrusted control sphere to be include…KEVEPSS 64%analysed7.8CVE-2025-32463Sudo chroot local privilege escalation via untrusted nsswitch.confSudo before 1.9.17p1 loads /etc/nsswitch.conf from a user-controlled directory when the --chroot option is used, allowing inclusion of functionality …KEVEPSS 61%analysed

Source: NIST National Vulnerability Database (record CVE-2026-66843), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.