An authentication bypass vulnerability in libcurl allows for potential credential leakage between sequential proxy transfers, posing a critical risk of unauthorized data access.

This is a capture-replay authentication bypass (CWE-294) where libcurl fails to clear proxy credentials when reusing a handle. This allows an unauthenticated attacker to potentially intercept or redirect authentication data during subsequent requests.

The exploitation of this flaw could lead to the unauthorized exposure of sensitive proxy credentials, facilitating lateral movement or man-in-the-middle attacks. Given the CVSS score of 9.1, this vulnerability presents a critical threat to data confidentiality and integrity, particularly in environments utilizing automated proxy-based traffic routing.

Immediate Action: Update the curl library to the latest available version provided by the vendor.

Proactive Monitoring: Review proxy and application access logs for unusual authentication patterns or failed connection attempts following authentication.

Compensating Controls: Implement network-level segmentation to limit the reach of proxy servers and utilize encrypted tunnels where possible to reduce the impact of potential credential exposure.

Public Exploit Available: Unknown

The severity of this issue necessitates immediate patching. Organizations relying on libcurl for automated transfers must prioritize updating their environments to the latest stable release to eliminate the risk of credential interception.