Horizon Alert
Summary of the vulnerability and why it matters
This advisory addresses a security vulnerability where an HTTP proxy could trick libcurl into sending sensitive credentials, such as passwords or authentication tickets, to the proxy itself rather than the intended destination. This could potentially expose authentication information that should remain private. The main concern is confirming relevance and exposure within our environment.
- Credentials can be intercepted by proxies.
- Protects sensitive authentication data.
- Confirm if we use affected technology.
Attack Path
How an attacker could exploit the issue
An attacker could trick a system using libcurl into revealing its authentication details to a malicious HTTP proxy. This happens when the proxy incorrectly responds to a connection request, causing libcurl to send sensitive information, such as passwords or authentication tickets, directly to the proxy instead of handling it properly. This could allow an attacker controlling a proxy to gain unauthorized access to the origin system.
- No specific access required.
- Proxy sends a misleading authentication challenge.
- Credentials leaked to an attacker-controlled proxy.
Live Threat
Current exploitation, exposure, and threat context
When an HTTP proxy responds unexpectedly to a `CONNECT` request, it could trick libcurl into sending the origin's credentials, such as passwords or authentication tickets, directly to the proxy itself. This could occur when the proxy sends a 401 `WWW-Authenticate:` header instead of the expected 407 `Proxy-Authenticate:`, potentially exposing sensitive authentication information.
- Origin server credentials.
- Proxy intercepts authentication data.
- Unauthorized access to origin services.
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability in libcurl could lead to the exposure of sensitive credentials to an attacker-controlled proxy. Initial triage should focus on identifying all instances of libcurl within the environment, assessing their reachability and business criticality, and determining the accountable application or service owners. Planning for remediation or mitigation should then proceed based on the identified risk, potentially involving coordination with upstream application teams or vendors.
- Application and platform teams should own the issue.
- Verify libcurl usage and proxy reachability.
- Plan remediation based on risk assessment.
