CVE-2026-66370
html_sanitize_ex HTML5 scrubber keeps attacker-supplied form-association attributes, allowing form hijacking
Description
URL Redirection to Untrusted Site ('Open Redirect') 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 <input> element in sanitized HTML. HTML'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's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing. 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. This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.
INFO
Published Date :
Aug. 6, 2026, 4:16 p.m.
Last Modified :
Aug. 6, 2026, 4:16 p.m.
Remotely Exploit :
Yes !
Source :
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Affected Products
The following products are affected by CVE-2026-66370
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | ||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
Solution
- Update html_sanitize_ex to version 1.5.3 or newer.
- Ensure input elements do not use the formaction attribute.
- Validate all external URLs before processing them.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-66370.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-66370 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-66370
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-66370 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-66370 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Aug. 06, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/rrrene/html_sanitize_ex', 'vendor': 'rrrene', 'modules': ['Elixir.HtmlSanitizeEx.Scrubber.HTML5', 'Elixir.HtmlSanitizeEx'], 'product': 'html_sanitize_ex', 'versions': [{'status': 'affected', 'version': '0.3.1', 'lessThan': '1.5.3', 'versionType': 'semver'}], 'packageURL': 'pkg:hex/html_sanitize_ex', 'packageName': 'html_sanitize_ex', 'programFiles': ['lib/html_sanitize_ex/scrubber/html5.ex', 'lib/html_sanitize_ex.ex'], 'collectionURL': 'https://repo.hex.pm', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"}, {'name': "'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"}, {'name': "'Elixir.HtmlSanitizeEx':html5/1"}]}, {'cpes': ['cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/rrrene/html_sanitize_ex', 'vendor': 'rrrene', 'modules': ['Elixir.HtmlSanitizeEx.Scrubber.HTML5', 'Elixir.HtmlSanitizeEx'], 'product': 'html_sanitize_ex', 'versions': [{'status': 'affected', 'version': '8976d64ea0b77d26093a94a43ec48a3978e8d028', 'lessThan': 'a1e804ed997e780ea71d14393cf2f701330553a6', 'versionType': 'git'}], 'packageURL': 'pkg:github/rrrene/html_sanitize_ex', 'packageName': 'rrrene/html_sanitize_ex', 'programFiles': ['lib/html_sanitize_ex/scrubber/html5.ex', 'lib/html_sanitize_ex.ex'], 'collectionURL': 'https://github.com', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"}, {'name': "'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"}, {'name': "'Elixir.HtmlSanitizeEx':html5/1"}]}] Added Description URL Redirection to Untrusted Site ('Open Redirect') 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 <input> element in sanitized HTML. HTML'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's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing. 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. This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/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:X/V:X/RE:X/U:X Added CWE CWE-601 Added Reference https://cna.erlef.org/cves/CVE-2026-66370.html Added Reference https://github.com/rrrene/html_sanitize_ex/commit/a1e804ed997e780ea71d14393cf2f701330553a6 Added Reference https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-w3f9-jjhw-wwvq Added Reference https://osv.dev/vulnerability/EEF-CVE-2026-66370