CVE-2026-23956
Published: 22 January 2026
Summary
CVE-2026-23956 is a high-severity Inefficient Regular Expression Complexity (CWE-1333) vulnerability in Lxsmnsyc Seroval. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 21.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SC-5 (Denial-of-service Protection).
Deeper analysis
CVE-2026-23956 affects the seroval JavaScript library, which enables stringification of JavaScript values including complex structures beyond the capabilities of JSON.stringify. In versions 1.4.0 and earlier, the vulnerability arises from overriding RegExp serialization with extremely large patterns, which can exhaust JavaScript runtime memory during deserialization. Additionally, patterns that trigger catastrophic backtracking can cause ReDoS (Regular Expression Denial of Service). The issue is classified under CWE-1333 with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Attackers can exploit this vulnerability remotely over the network with low complexity, requiring no privileges, authentication, or user interaction. By crafting malicious serialized payloads with oversized or backtracking-prone RegExp patterns, unauthenticated attackers can trigger memory exhaustion or prolonged CPU usage during deserialization, resulting in denial of service that disrupts application availability.
The seroval security advisory and associated commit confirm the issue has been addressed in version 1.4.1. Security practitioners should upgrade to this patched version to mitigate the vulnerability, as detailed in the GitHub security advisory (GHSA-hx9m-jf43-8ffr) and the fixing commit (ce9408ebc87312fcad345a73c172212f2a798060).
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-3669
Vulnerability details
seroval facilitates JS value stringification, including complex structures beyond JSON.stringify capabilities. In versions 0.2.0 through 1.4.0, overriding RegExp serialization with extremely large patterns can exhaust JavaScript runtime memory during deserialization. Additionally, overriding RegExp serialization with patterns that trigger catastrophic backtracking…
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can lead to ReDoS (Regular Expression Denial of Service). This issue has been fixed in version 1.4.1.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct remote exploitation of library deserialization flaw (oversized/backtracking RegExp) to trigger memory/CPU exhaustion and application DoS.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires applying the vendor patch (upgrade to seroval 1.4.1) that eliminates the RegExp memory-exhaustion and ReDoS flaws.
Requires validation of deserialized input to reject oversized or catastrophic-backtracking RegExp patterns before they reach seroval.
Mandates technical controls that limit resource exhaustion from untrusted serialization payloads, mitigating the resulting denial-of-service.