CVE-2024-50342 in Symfony
Summary
by MITRE • 11/06/2024
symfony/http-client is a module for the Symphony PHP framework which provides powerful methods to fetch HTTP resources synchronously or asynchronously. When using the `NoPrivateNetworkHttpClient`, some internal information is still leaking during host resolution, which leads to possible IP/port enumeration. As of versions 5.4.46, 6.4.14, and 7.1.7 the `NoPrivateNetworkHttpClient` now filters blocked IPs earlier to prevent such leaks. All users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 01/13/2026
The vulnerability identified as CVE-2024-50342 affects the symfony/http-client module within the Symfony PHP framework, specifically impacting the NoPrivateNetworkHttpClient component. This module serves as a critical HTTP client implementation that enables applications to fetch resources either synchronously or asynchronously, making it a fundamental building block for web applications that require external HTTP communication. The flaw manifests in how the client handles host resolution processes when operating under the NoPrivateNetworkHttpClient configuration, which is designed to prevent access to private network addresses and mitigate potential internal network reconnaissance attacks.
The technical implementation flaw lies in the timing of IP address filtering within the host resolution process. While the NoPrivateNetworkHttpClient was intended to block access to private network ranges such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, the vulnerability allows for information leakage during DNS resolution and connection establishment phases. This occurs because internal IP addresses that should be blocked are still being processed and potentially exposed through various network stack behaviors, including DNS query responses, connection attempts, or error messages that reveal network topology information. The vulnerability represents a weakness in the principle of least privilege and defense in depth within the HTTP client's network access controls.
The operational impact of this vulnerability extends beyond simple information disclosure, creating potential attack vectors for network enumeration and reconnaissance activities. An attacker could leverage this flaw to perform IP/port enumeration against systems that utilize the affected Symfony HttpClient component, potentially discovering internal network structure, active services, or vulnerable endpoints that should remain hidden. This information leakage could enable more sophisticated attacks such as port scanning, service fingerprinting, or even privilege escalation attempts if internal systems are discovered to be running vulnerable software or services. The vulnerability particularly affects applications that process untrusted input or external URLs, as these scenarios would trigger the problematic host resolution behavior.
Organizations using Symfony applications that incorporate the http-client module are strongly advised to upgrade to versions 5.4.46, 6.4.14, or 7.1.7, which implement early filtering of blocked IP addresses during the host resolution process. This mitigation addresses the root cause by ensuring that private network addresses are filtered before any network activity occurs, preventing the information leakage that could enable enumeration attacks. The lack of known workarounds means that administrators must rely on upgrading the framework components rather than implementing temporary fixes or patches. Security practitioners should consider this vulnerability in the context of broader network security practices and ensure that applications utilizing this component are properly monitored for any signs of enumeration attempts or unauthorized network access patterns.
This vulnerability aligns with CWE-200 (Information Exposure) and CWE-693 (Protection Mechanism Failure) classifications, demonstrating how security controls can fail during implementation phases. The issue also maps to ATT&CK technique T1046 (Network Service Scanning) and T1083 (File and Directory Discovery) where attackers could leverage the information leakage for further reconnaissance. The fix implemented in the patched versions represents a proper security control implementation that addresses the timing issue in the network access control mechanism, ensuring that all network activity is properly filtered before any communication occurs. Organizations should verify their deployments and ensure that all instances of the affected Symfony HttpClient components are updated to prevent potential exploitation of this information disclosure vulnerability.