CVE-2010-0010 in HTTP Server
Summary
by MITRE
Integer overflow in the ap_proxy_send_fb function in proxy/proxy_util.c in mod_proxy in the Apache HTTP Server before 1.3.42 on 64-bit platforms allows remote origin servers to cause a denial of service (daemon crash) or possibly execute arbitrary code via a large chunk size that triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2010-0010 represents a critical integer overflow flaw within the Apache HTTP Server's mod_proxy module, specifically affecting versions prior to 1.3.42 on 64-bit systems. This issue resides in the ap_proxy_send_fb function located in proxy/proxy_util.c, which handles the forwarding of data through proxy connections. The flaw manifests when remote origin servers provide excessively large chunk size values that exceed the expected integer limits, creating a dangerous condition that can be exploited for both denial of service and potential code execution.
The technical mechanism behind this vulnerability involves an integer overflow occurring during the processing of HTTP chunked transfer encoding. When the proxy module receives a chunked response from an origin server, it attempts to calculate buffer sizes based on the chunk size values provided in the HTTP headers. On 64-bit platforms, the integer overflow causes the calculated buffer size to wrap around to a small value, while the actual data being processed remains large. This discrepancy results in a heap-based buffer overflow where the system attempts to write more data into a buffer than allocated, potentially corrupting adjacent memory regions and leading to unpredictable behavior.
The operational impact of this vulnerability extends beyond simple service disruption, as it presents a potential path for remote code execution. Attackers can craft malicious responses with carefully constructed chunk sizes that trigger the overflow condition, causing the Apache daemon to crash or potentially allowing arbitrary code execution if the overflow corrupts critical memory structures. The vulnerability affects the core proxy functionality of Apache, making it particularly dangerous for servers that rely on proxy capabilities for load balancing, content filtering, or reverse proxy operations. This makes the flaw especially concerning for enterprise environments where Apache serves as a critical component in web infrastructure.
Security professionals should recognize this vulnerability as aligning with CWE-190, Integer Overflow or Wraparound, and CWE-121, Stack-based Buffer Overflow, while also mapping to ATT&CK technique T1499.004, Endpoint Denial of Service, and T1059.001, Command and Scripting Interpreter. The vulnerability demonstrates the importance of proper input validation and integer overflow protection in network services, particularly those handling untrusted data from external sources. Organizations should prioritize immediate patching of affected Apache installations to prevent exploitation, while implementing network monitoring to detect suspicious chunked transfer encoding patterns that might indicate attempted exploitation attempts. Additionally, defensive measures including proxy configuration restrictions and input sanitization should be considered as part of comprehensive mitigation strategies to protect against similar vulnerabilities in the future.