CVE-2026-106104: CWE-1333: Inefficient Regular Expression Complexity in quasarframework quasar
Description
Quasar Framework versions prior to 2.23.3 contain an inefficient regular expression complexity vulnerability in the Platform.parseSSR() function. This vulnerability arises from unbounded User-Agent header parsing that triggers super-linear backtracking, causing the Node.js event loop to block and delay all server-side rendering (SSR) requests. This affects only SSR targets and not SPA, PWA, Electron, Cordova, Capacitor, browser-extension, or static-site-generation targets. The issue is fixed in version 2.23.3.
CVSS v4.0
Score 8.7high
Affected software
quasarframework
quasar
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability (CVE-2026-106104) in quasarframework's quasar product involves inefficient regular expression complexity (CWE-1333) in the Platform.parseSSR() method prior to version 2.23.3. The method passes an unbounded User-Agent header to a regex matching function that uses greedy captures combined with repeated unbounded scans. An attacker can craft a User-Agent header with repeated version tokens lacking a terminating Safari token, causing super-linear backtracking. This backtracking blocks the Node.js event loop, delaying all SSR requests. Non-SSR targets are unaffected. The vulnerability is resolved in quasar version 2.23.3.
Potential Impact
An unauthenticated attacker can send a specially crafted User-Agent header to cause super-linear regex backtracking in the SSR request parsing, blocking the Node.js event loop. This results in denial of service by delaying or blocking all SSR requests on the affected server. Other application targets that do not parse the User-Agent header in this manner are not impacted.
Mitigation Recommendations
Upgrade quasarframework quasar to version 2.23.3 or later, where this vulnerability is fixed. No other mitigations are indicated. Patch status is confirmed as an official fix in version 2.23.3.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-10-06T15:33:55.333Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ac5310f2cdf04f656ca0fbb
Added to database: 10/06/2026, 17:34:07 UTC
Last enriched: 10/06/2026, 17:48:18 UTC
Last updated: 10/06/2026, 17:49:12 UTC
Views: 3
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