curl Credential Leak via .netrc Misconfiguration

Mitigation Strategies

The primary mitigation is to upgrade curl to version 8.21.0 or later, where this vulnerability has been fixed.

Alternatively, apply the official patch provided by the curl project if upgrading is not immediately possible.

As a temporary workaround, avoid using the .netrc file for storing authentication data when specifying URLs with usernames but no passwords.

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Executive Summary

CVE-2026-8926 is a vulnerability in curl versions 8.11.1 through 8.20.0 where curl, when instructed to use a .netrc file for credentials and simultaneously given a URL with a username but no password, could mistakenly use the password of a different user from the .netrc file for that host if the specified user does not have a matching entry.

This flaw is classified under CWE-522, indicating insufficiently protected credentials, and arises from improper handling of authentication data.

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Impact Analysis

This vulnerability can lead to unintended password leaks by causing curl to use the wrong user's password from the .netrc file when authenticating to a host.

Such leaks could allow unauthorized access to services or data if an attacker gains access to the misused credentials.

The severity of this issue is considered low, but it still poses a risk of credential exposure.

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Detection Guidance

This vulnerability occurs when curl versions 8.11.1 through 8.20.0 use a .netrc file for credentials and a URL with a username but no password is specified. Detection involves identifying usage of vulnerable curl versions and commands that combine .netrc authentication with URLs containing usernames without passwords.

You can check the curl version on your system with the command: `curl --version`.

To detect if vulnerable commands are being used, look for curl invocations that specify a username in the URL without a password, for example: `curl https://[email protected]/`.

Monitoring network traffic for unexpected credential leaks or unusual authentication attempts related to curl usage may also help detect exploitation.

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Compliance Impact

CVE-2026-8926 involves the improper handling of authentication credentials in curl, potentially exposing passwords stored in the .netrc file to unauthorized use. This kind of credential leakage can lead to unauthorized access to sensitive data.

Such exposure of credentials may impact compliance with standards and regulations like GDPR and HIPAA, which require protection of personal and sensitive information, including secure handling of authentication data.

Organizations using vulnerable versions of curl could face increased risk of data breaches or unauthorized access, which may result in non-compliance with these regulations if sensitive data is compromised.

To mitigate this risk and maintain compliance, affected users are advised to upgrade to curl version 8.21.0 or later, apply patches, or avoid using .netrc files for storing authentication credentials.

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