CVE-2015-1380 in Privoxy
Summary
by MITRE
jcc.c in Privoxy before 3.0.23 allows remote attackers to cause a denial of service (abort) via a crafted chunk-encoded body.
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Analysis
by VulDB Data Team • 04/12/2022
The vulnerability identified as CVE-2015-1380 affects Privoxy version 3.0.22 and earlier, representing a critical denial of service flaw within the HTTP proxy software's chunked transfer encoding handling mechanism. This vulnerability resides in the jcc.c source file, which processes chunked encoding data streams that are commonly used in HTTP communications to transmit data in chunks rather than as a single continuous stream. The flaw manifests when Privoxy encounters specifically crafted chunk-encoded bodies that exploit improper validation of chunk size parameters and data boundaries within the chunked transfer encoding protocol implementation.
The technical exploitation of this vulnerability occurs through the manipulation of chunked transfer encoding data where attackers craft malicious chunk headers containing invalid or malformed chunk sizes that cause the Privoxy proxy to encounter unexpected behavior during data processing. When the proxy attempts to parse these crafted chunked bodies, it triggers an abort condition in the jcc.c processing module, resulting in the termination of the proxy service and complete denial of service for all users relying on that proxy instance. This represents a classic buffer over-read or parsing error condition where the software fails to properly validate input data before attempting to process it, leading to an abrupt program termination rather than graceful error handling.
From an operational impact perspective, this vulnerability creates a significant risk for organizations relying on Privoxy as a web proxy solution, particularly in environments where continuous availability is critical. The denial of service condition can be easily triggered by remote attackers without requiring authentication or special privileges, making it an attractive target for attackers seeking to disrupt services. The vulnerability affects the core functionality of Privoxy's HTTP processing capabilities, potentially impacting web browsing, content filtering, and proxy-based network access for all users connected through the affected proxy server. This type of vulnerability directly impacts the availability aspect of the CIA triad and can be leveraged as part of broader attack campaigns targeting network infrastructure.
The vulnerability aligns with CWE-129, which describes improper validation of input boundaries, and represents a classic example of insufficient input validation in network protocol handling code. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, where attackers leverage application-level flaws to disrupt service availability. Organizations should prioritize immediate patching of affected Privoxy installations to address this vulnerability, as the fix in version 3.0.23 includes proper validation of chunked encoding parameters and enhanced error handling to prevent the abort condition. Additional mitigations include implementing network-level filtering to restrict chunked transfer encoding traffic when not required, deploying intrusion detection systems to monitor for exploitation attempts, and establishing redundant proxy infrastructure to minimize impact from such attacks.