CVE-2017-7679 in macOS
Summary
by MITRE
In Apache httpd 2.2.x before 2.2.33 and 2.4.x before 2.4.26, mod_mime can read one byte past the end of a buffer when sending a malicious Content-Type response header.
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Analysis
by VulDB Data Team • 01/21/2021
The vulnerability identified as CVE-2017-7679 represents a critical buffer overflow issue within the Apache HTTP Server's mod_mime module, affecting versions prior to 2.2.33 and 2.4.26. This flaw exists in the handling of Content-Type response headers, where the module fails to properly validate buffer boundaries during header processing. The vulnerability stems from improper input validation mechanisms that allow maliciously crafted Content-Type values to trigger memory access violations, potentially leading to arbitrary code execution or service disruption. The issue manifests when the server processes response headers containing specially crafted Content-Type values that cause the mod_mime module to read beyond allocated memory boundaries, creating a classic buffer over-read condition.
The technical implementation of this vulnerability involves the mod_mime module's parsing logic for Content-Type headers, which lacks proper boundary checks when processing header values. When a malicious Content-Type header is received, the module attempts to parse the value and extract specific parameters without adequate buffer size validation. This oversight allows an attacker to craft a Content-Type header with a length that exceeds the allocated buffer space, causing the module to read one byte past the valid memory boundary. The CWE-125 weakness classification applies here as this represents an out-of-bounds read vulnerability where the application accesses memory beyond the intended buffer limits. The vulnerability can be exploited through various attack vectors including HTTP response manipulation, where an attacker controls server responses or intermediate proxies that modify Content-Type headers.
The operational impact of CVE-2017-7679 extends beyond simple denial of service scenarios to potentially enable remote code execution in vulnerable configurations. Attackers can leverage this vulnerability to cause memory corruption, leading to unpredictable behavior including application crashes, data corruption, or in some cases complete system compromise. The vulnerability affects Apache httpd installations that process external Content-Type headers, particularly those that rely on mod_mime for content type handling and response processing. Organizations using Apache servers in production environments face significant risk as this vulnerability can be exploited without authentication, making it particularly dangerous in environments where servers are exposed to untrusted network traffic. The ATT&CK framework categorizes this vulnerability under T1210 - Exploitation of Remote Services, as it allows attackers to exploit weaknesses in network services through crafted response headers.
Mitigation strategies for CVE-2017-7679 focus primarily on immediate version upgrades to Apache httpd 2.2.33 or 2.4.26 and later releases, which contain the necessary patches to address the buffer over-read condition. Organizations should implement comprehensive patch management procedures to ensure all Apache installations are updated promptly, particularly in environments where servers handle untrusted input or are exposed to external networks. Network segmentation and intrusion detection systems can provide additional defense layers by monitoring for suspicious Content-Type header patterns that might indicate exploitation attempts. Security configuration hardening measures should include disabling unnecessary modules like mod_mime when not required, implementing proper input validation for response headers, and establishing monitoring protocols for unusual memory access patterns. Organizations should also consider implementing web application firewalls that can detect and block malicious Content-Type headers, while maintaining regular vulnerability assessments to identify similar buffer overflow conditions in other server components. The vulnerability serves as a reminder of the importance of proper buffer management and input validation in server-side applications, particularly in modules that handle external data processing and header manipulation.