VDB-399418 · CVE-2026-86205 · EUVD-2026-72105

h3js h3 up to 2.0.1-rc.17 Redirect Utility redirectBack

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
4.7	$0-$5k	2.50+

Summaryinfo

A vulnerability described as problematic has been identified in h3js h3 up to 2.0.1-rc.17. This affects the function redirectBack of the component Redirect Utility. Executing a manipulation can lead to redirect. This vulnerability appears as CVE-2026-86205. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in h3js h3 up to 2.0.1-rc.17. It has been declared as problematic. This vulnerability affects the function redirectBack of the component Redirect Utility. The manipulation with an unknown input leads to a redirect vulnerability. The CWE definition for the vulnerability is CWE-601. A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks. As an impact it is known to affect integrity. CVE summarizes:

h3 versions before 2.0.1-rc.18 contain an open redirect vulnerability in the redirectBack() utility that fails to sanitize protocol-relative paths in the Referer header pathname. Attackers can craft a same-origin URL with a double-slash path segment that passes origin validation but produces a Location header interpreted by browsers as a protocol-relative redirect to an external domain.

The advisory is available at github.com. This vulnerability was named CVE-2026-86205 since 09/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1204.001 by the MITRE ATT&CK project.

Upgrading to version 2.0.1-rc.18 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-72105). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

h3js

Name

Version

Website

Product: https://github.com/h3js/h3/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 4.8
VulDB Meta Temp Score: 4.7

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.4
CNA Vector (VulnCheck): 🔒

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Redirect
CWE: CWE-601
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: h3 2.0.1-rc.18

Timelineinfo

09/05/2026 CVE reserved
09/06/2026 +1 days Advisory disclosed
09/06/2026 +0 days VulDB entry created
09/06/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Confirmed

CVE: CVE-2026-86205 (🔒)
GCVE (CVE): GCVE-0-2026-86205
GCVE (VulDB): GCVE-100-399418
EUVD: 🔒

Entryinfo

Created: 09/06/2026 14:21
Updated: 09/06/2026 16:57
Changes: 09/06/2026 14:21 (77), 09/06/2026 16:57 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.