CVE-2020-26302: 
JavaScript vulnerability analysis and mitigation

CVE-2020-26302 affects is.js, a general-purpose check library, in versions 0.9.0 and prior. The vulnerability involves a Regular Expression Denial of Service (ReDoS) issue in the URL validation functionality. The vulnerability was discovered using a CodeQL query that identifies inefficient regular expressions (GitHub SecLab, NVD).

The vulnerability stems from poorly constructed regular expressions used for URL validation. The regex implementation can exhibit O(2^n) runtime performance due to exponential backtracking when processing certain malicious input strings. The vulnerability was assigned a CVSS v3.1 Base Score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (GitHub SecLab).

The vulnerability can lead to a denial of service condition when processing maliciously crafted input. When the affected URL validation function processes certain specially crafted strings, it can cause the application to enter an extremely long processing loop, effectively making the service unavailable (GitHub SecLab).

No official patch has been released for this vulnerability. The general approach to fixing ReDoS vulnerabilities involves removing ambiguity and overlap within the regular expression patterns (GitHub SecLab).