PatchSiren cyber security CVE debrief

CVE-2025-13826 Zervit CVE debrief

A remote denial-of-service vulnerability exists in Zervit's portable HTTP/web server. The flaw stems from insufficient validation of user-supplied input during configuration reset requests. An unauthenticated attacker can exploit this by sending malicious requests to trigger a DoS condition, requiring manual application restart to restore service. The vulnerability was published on 2026-04-21 and last modified on 2026-05-19. No known exploitation in ransomware campaigns has been documented, and the vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog.

Vendor: Zervit
Product: portable HTTP/Web server
CVSS: HIGH 8.2
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-04-21
Original CVE updated: 2026-05-19
Advisory published: 2026-04-21
Advisory updated: 2026-05-19

Who should care

Organizations running Zervit portable HTTP/web server in production environments, particularly those with exposed management or configuration interfaces. Security teams responsible for availability of web services and infrastructure operators relying on Zervit for lightweight HTTP serving should prioritize assessment and remediation.

Technical summary

The vulnerability exists in the configuration reset functionality of Zervit's portable HTTP/web server. Insufficient validation of user-supplied input allows remote, unauthenticated attackers to send crafted requests that cause the application to stop responding. Successful exploitation results in a denial-of-service condition that can only be resolved through manual application restart. The attack requires network access to the server but no authentication or user interaction.

Defensive priority

high

Recommended defensive actions

Apply input validation to configuration reset endpoints
Implement rate limiting on administrative functions
Monitor for anomalous request patterns to configuration interfaces
Review and restrict network exposure of Zervit management interfaces
Establish automated health checks and restart procedures for service availability

Evidence notes

The vulnerability description indicates inadequate input validation (CWE-20) as the root cause. The CVSS 4.0 vector confirms network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), and high availability impact (VA:H). The vendor attribution is marked as low confidence based on reference domain analysis pointing to INCIBE.

Official resources

CVE-2025-13826 was published on 2026-04-21 and modified on 2026-05-19. The vulnerability affects Zervit's portable HTTP/web server and carries a CVSS 4.0 score of 8.2 (HIGH severity). The issue was reported through INCIBE-CERT, the Spanish'