CVE-2026-8926 in cURL
Summary
by MITRE • 07/03/2026
When asking curl to use a `.netrc` file to find credentials and at the same time specifying a URL with a username(without a password), like `https://[email protected]/`, curl could wrongly get and use the password for *another* user set in the `.netrc` file for that host if such a one exists and there is no match for the specified user.
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Analysis
by VulDB Data Team • 07/04/2026
This vulnerability involves a critical credential handling flaw in curl's authentication mechanism when processing .netrc files alongside URL-based credentials. The issue occurs when curl attempts to authenticate using a .netrc file for host credentials while simultaneously receiving a URL containing a username but no password component. The software fails to properly validate that the username specified in the URL matches the credentials retrieved from the .netrc file, creating a potential authentication bypass scenario.
The technical implementation flaw stems from curl's insufficient credential matching logic during the authentication process. When a URL contains a username such as https://[email protected]/, curl should verify that this specific user account corresponds to the credentials found in the .netrc file for that host. However, the software incorrectly processes the .netrc file and may select a password for a different user account that shares the same hostname but has a different username. This behavior violates fundamental security principles of credential isolation and authentication context validation.
The operational impact of this vulnerability is significant as it enables unauthorized access to systems where curl is used for automated operations or script-based interactions. An attacker could potentially exploit this flaw in scenarios where legitimate users rely on .netrc files for credential management while also using URL-based authentication. The vulnerability creates a pathway for privilege escalation or unauthorized data access when curl processes multiple credential sources without proper validation of user context.
This issue relates to CWE-287, which addresses improper authentication vulnerabilities, and aligns with ATT&CK technique T1566 for credential access through compromised authentication mechanisms. The flaw represents a failure in input validation and credential verification within the application's authentication flow, potentially allowing attackers to leverage one user's credentials to access another user's resources on the same host system.
Organizations should implement immediate mitigations including updating curl to versions that address this specific credential matching vulnerability, reviewing .netrc file permissions to prevent unauthorized modifications, and implementing strict credential management policies. Additionally, administrators should consider disabling automatic .netrc file usage in sensitive environments and instead require explicit credential specification through command-line options or environment variables. The recommended approach involves configuring curl with explicit authentication parameters and avoiding mixed credential sources that could trigger this validation bypass condition.