CVE-2017-7375 in libxml2
Summary
by MITRE
A flaw in libxml2 allows remote XML entity inclusion with default parser flags (i.e., when the caller did not request entity substitution, DTD validation, external DTD subset loading, or default DTD attributes). Depending on the context, this may expose a higher-risk attack surface in libxml2 not usually reachable with default parser flags, and expose content from local files, HTTP, or FTP servers (which might be otherwise unreachable).
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Analysis
by VulDB Data Team • 12/04/2025
The vulnerability identified as CVE-2017-7375 represents a significant security flaw within the libxml2 library that processes xml data. This issue specifically targets the default parser behavior where certain security protections are not enabled by default, creating an unexpected attack vector that could be exploited by remote adversaries. The vulnerability manifests when the parser operates with its standard configuration settings, which do not include explicit restrictions on entity processing or external resource access. This default configuration leaves applications using libxml2 exposed to malicious xml content that can trigger unintended behavior during parsing operations.
The technical implementation of this vulnerability stems from how libxml2 handles xml entity resolution during parsing operations. When the parser encounters external entities or references within xml documents, it can automatically resolve these references even when the application has not explicitly requested such behavior. This flaw is particularly dangerous because it operates under default parser flags that are commonly used by applications without explicit security configuration. The vulnerability allows attackers to craft malicious xml content that can cause the parser to access local files, http resources, or ftp servers through the entity resolution mechanism. This behavior occurs regardless of whether the application specifically requested entity substitution or DTD validation, making it a particularly insidious issue that can be exploited across a wide range of applications.
The operational impact of CVE-2017-7375 extends beyond simple data exposure, as it can create a broader attack surface that might not normally be accessible through default parser configurations. Attackers can leverage this vulnerability to perform server-side request forgery attacks, potentially accessing internal resources that should be protected from external access. The vulnerability is particularly concerning because it can be exploited without requiring special privileges or specific application configurations that would normally be needed to enable such behavior. Applications that process untrusted xml data, including web services, content management systems, and any software that accepts xml input, could be compromised through this vulnerability. The exposure of local files through this mechanism could lead to sensitive data disclosure, while access to external servers could enable further reconnaissance or attack escalation.
Security mitigations for this vulnerability should focus on explicit configuration of parser settings to disable unwanted entity processing behaviors. Organizations should implement strict parser configurations that disable external entity resolution, DTD validation, and external DTD subset loading even when these features are not explicitly required by the application. The recommended approach involves setting appropriate parser flags to prevent automatic entity substitution and limiting access to external resources during xml parsing operations. Additionally, applications should validate and sanitize all xml input before processing, implementing proper input validation techniques that can detect and reject potentially malicious xml content. This vulnerability aligns with CWE-611, which describes improper access control in xml processing, and maps to ATT&CK technique T1213.002 for data from information repositories, as it enables unauthorized access to system resources through xml parsing mechanisms. The vulnerability demonstrates how default security settings in widely-used libraries can create unexpected attack vectors that require explicit configuration changes to address properly.