Information disclosure due to uncleared proxy authentication state

Summary

When reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration, libcurl fails to clear the proxy authentication state between requests. Specifically, if the initial transfer authenticates against `proxyA` using Digest auth, a subsequent transfer routed through `proxyB` erroneously leaks the `Proxy-Authorization:` header intended solely for `proxyA`. A flaw was found in libcurl. When reusing a libcurl handle for sequential transfers with environment-variable proxy configuration, the library does not properly clear the proxy authentication state. This oversight can lead to the unintended disclosure of `Proxy-Authorization` headers to an incorrect proxy, potentially exposing sensitive authentication information to an unauthorized entity. This is an information disclosure vulnerability. This Important information disclosure vulnerability in libcurl arises when a handle is reused for sequential transfers with environment-variable proxy configurations, failing to clear the proxy authentication state. This oversight can lead to `Proxy-Authorization` headers being inadvertently sent to an incorrect proxy, potentially exposing sensitive authentication information in Red Hat environments utilizing multiple proxy configurations. This flaw leads only to a confidentiality impact. There has been no observed integrity impact. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N). Weakness: CWE-201. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.