A critical connection reuse vulnerability in libcurl allows unauthenticated attackers to potentially hijack authenticated sessions, posing a severe risk to data confidentiality and integrity.

This vulnerability involves an exposure of data elements to the wrong session (CWE-488), where libcurl incorrectly reuses an existing authenticated connection for a new, unauthenticated request. Because this occurs at the library level, it affects any application utilizing libcurl for network communication when Negotiate authentication is enabled.

The potential impact of this flaw is severe, as it enables unauthorized access to sensitive data transmitted over hijacked connections. With a CVSS score of 9.8, the vulnerability is classified as critical because it allows for full compromise of confidentiality, integrity, and availability without requiring user interaction or authentication. Organizations relying on curl for internal service communication or API integrations face significant risks of lateral movement and data exfiltration.

Immediate Action: Organizations should identify applications utilizing the affected versions of libcurl and prepare to update to the next available secure release as soon as it is published by the vendor.

Proactive Monitoring: Security teams should monitor application logs and network traffic for unusual authentication patterns or unexpected session data being associated with different user identities.

Compensating Controls: Deploying a Web Application Firewall (WAF) or enforcing strict mTLS configurations may help mitigate the risk by preventing unauthorized connections, although these are not direct fixes for the library-level flaw.

Public Exploit Available: Unknown

Given the critical CVSS severity and the confirmed presence of a proof-of-concept, this vulnerability warrants immediate attention. IT administrators must prioritize patching all instances of the affected libcurl versions as soon as the vendor provides a remediation release, as the potential for session hijacking presents a significant threat to organizational security posture.