CVE-2026-66370

Severity CVSS v4.0:

MEDIUM

Type:

CWE-601 URL Redirection to Untrusted Site ('Open Redirect')

Publication date:

06/08/2026

Last modified:

11/08/2026

Description

URL Redirection to Untrusted Site (&#39;Open Redirect&#39;) vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the form and formaction attributes on an element in sanitized HTML. HTML&#39;s form attribute associates an input with any form on the page by its id even when the input sits outside that form, and formaction on a submit control overrides the owning form&#39;s action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing.<br /> <br /> No script executes. The scrubber allows neither form nor button, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an id.<br /> <br /> This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.

Impact

Vector 4.0

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N CVSS v4.0 Severity and Metrics:

Base Score: 4.80 MEDIUM
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Attack Requirements (AT): Present
Privileges Required (PR): None
User Interaction (UI): Active
Confidentiality (VC): None
Integrity (VI): None
Availability (VA): None
Confidentiality (SC): High
Integrity (SI): Low
Availability (SA): None

Base Score 4.0

4.80

Severity 4.0

MEDIUM

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N CVSS v3.1 Severity and Metrics:

Base Score: 6.10 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): Required
Scope (S): Changed
Confidentiality (C): Low
Integrity (I): Low
Availability (A): None