CVE-2026-22809: tarteaucitron.js ReDoS Vulnerability

CVE-2026-22809 Overview

A Regular Expression Denial of Service (ReDoS) vulnerability has been identified in tarteaucitron.js, a compliant and accessible cookie banner solution. The vulnerability exists in the handling of the issuu_id parameter in versions prior to 1.29.0. An attacker can exploit this flaw by providing specially crafted input that causes catastrophic backtracking in the regular expression engine, leading to denial of service conditions.

Critical Impact

Exploitation of this ReDoS vulnerability can cause significant CPU resource exhaustion, rendering the affected web application unresponsive to legitimate users.

Affected Products

• tarteaucitron.js versions prior to 1.29.0

Discovery Timeline

• 2026-01-13 - CVE CVE-2026-22809 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2026-22809

Vulnerability Analysis

This vulnerability falls under CWE-1333 (Inefficient Regular Expression Complexity). The root cause lies in the use of a poorly designed regular expression pattern that is susceptible to catastrophic backtracking when processing malicious input. When the issuu_id parameter receives specially crafted strings, the regex engine enters an exponential-time matching scenario, consuming excessive CPU cycles and potentially causing the application to become unresponsive.

The vulnerability requires local access and high privileges to exploit, which limits the attack surface. However, in scenarios where an attacker can control or influence the issuu_id parameter, they can trigger the denial of service condition.

Root Cause

The vulnerability stems from an inefficient regular expression implementation in the tarteaucitron.js library. Regular expressions containing nested quantifiers or overlapping alternations are particularly susceptible to ReDoS attacks. When such patterns encounter adversarial input strings, the regex engine may need to explore an exponentially growing number of matching paths, leading to severe performance degradation.

Attack Vector

The attack requires local access with high privileges. An attacker would need to provide malicious input to the issuu_id parameter that triggers the vulnerable regular expression. The exploit leverages the exponential time complexity of certain regex patterns when processing strings specifically designed to maximize backtracking.

The security patch addressed this issue by removing vulnerable service integrations. The commit shows the removal of the alexa service integration which contained a vulnerable regex pattern:

     }
 };
 
-// alexa
-tarteaucitron.services.alexa = {
-    "key": "alexa",
-    "type": "analytic",
-    "name": "Alexa",
-    "uri": "https://www.alexa.com/help/privacy",
-    "needConsent": true,
-    "cookies": ['__asc', '__auc'],
-    "js": function () {
-        "use strict";
-        if (tarteaucitron.user.alexaAccountID === undefined) {
-            return;
-        }
-        window._atrk_opts = {
-            atrk_acct: tarteaucitron.user.alexaAccountID,
-            domain: window.location.hostname.match(/[^\.]*\.[^.]*$/)[0],
-            dynamic: true
-        };
-        tarteaucitron.addScript('https://d31qbv1cthcecs.cloudfront.net/atrk.js');
-    }
-};
-
 // amazon
 tarteaucitron.services.amazon = {
     "key": "amazon",

Source: GitHub Commit Update

Detection Methods for CVE-2026-22809

Indicators of Compromise

• Abnormal CPU utilization spikes on web servers running tarteaucitron.js
• Slow or unresponsive page loads when cookie consent banners are rendered
• Application logs showing extended processing times for requests involving the issuu_id parameter
• Web server timeout errors associated with JavaScript execution

Detection Strategies

• Monitor JavaScript execution time and flag anomalies exceeding normal thresholds
• Implement input validation to detect and block overly long or malformed issuu_id parameter values
• Use application performance monitoring (APM) tools to identify regex-related CPU bottlenecks
• Review dependency manifests to identify tarteaucitron.js versions below 1.29.0

Monitoring Recommendations

• Enable real-time CPU utilization monitoring on production web servers
• Configure alerting for sustained high CPU usage correlated with web traffic patterns
• Implement client-side performance monitoring to detect slow script execution
• Audit third-party JavaScript dependencies regularly for known vulnerabilities

How to Mitigate CVE-2026-22809

Immediate Actions Required

• Upgrade tarteaucitron.js to version 1.29.0 or later immediately
• Review application logs for evidence of exploitation attempts
• Implement input length restrictions on parameters processed by tarteaucitron.js
• Consider deploying a Web Application Firewall (WAF) rule to filter malicious input patterns

Patch Information

The vulnerability has been fixed in tarteaucitron.js version 1.29.0. The fix was implemented in commit f0bbdac2fdf3cd24a325fc0928c0d34abf1b7b52, which addresses the vulnerable regular expression patterns. Organizations should update to the patched version as soon as possible. For detailed information, refer to the GitHub Security Advisory.

Workarounds

• If immediate patching is not possible, implement server-side input validation to limit the length and character set of the issuu_id parameter
• Consider temporarily disabling or removing the vulnerable service integrations until the patch can be applied
• Deploy rate limiting to mitigate the impact of potential exploitation attempts
• Use a Content Security Policy (CSP) to restrict script execution contexts

# Update tarteaucitron.js using npm
npm update tarteaucitron

# Or install the specific patched version
npm install tarteaucitron@1.29.0