curl improperly reuses an existing HTTP proxy connection that performed a CONNECT operation, even when subsequent requests use different proxy credentials. This results in the proxy authentication data for one context being sent on a connection that should have been isolated, allowing an attacker to unintentionally expose credentials or bypass authentication controls. The weakness is identified as CWE-305, improper handling of credentials.

The vulnerability affects all versions of the curl client using the libcurl library, as indicated by the CPE cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:. No specific version range is provided in the CNA data, implying that any version prior to a fixed release is potentially impacted.

The severity is scored as a CVSS 6.5 (Medium), with an EPSS score of less than 1 % and the vulnerability is not listed in CISA’s KEV catalog. The likely attack vector is as follows: a skilled attacker that can control or influence the HTTP proxy used by a curl client could cause the client to send authentication credentials intended for a different proxy, resulting in credential leakage or unauthorized access. Exploitation does not appear to require privileged access to the client or server, and successful attacks would compromise confidentiality of proxy credentials and potentially lead to unauthorized data exfiltration.