CVE-2007-0157 in neon
Summary
by MITRE
Array index error in the uri_lookup function in the URI parser for neon 0.26.0 to 0.26.2, possibly only on 64-bit platforms, allows remote malicious servers to cause a denial of service (crash) via a URI with non-ASCII characters, which triggers a buffer under-read due to a type conversion error that generates a negative index.
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Analysis
by VulDB Data Team • 07/15/2019
The vulnerability identified as CVE-2007-0157 represents a critical array index error within the uri_lookup function of the neon library's URI parser version 0.26.0 through 0.26.2. This flaw specifically affects systems running 64-bit architectures and demonstrates a classic buffer under-read condition that can be exploited to cause remote denial of service. The vulnerability arises from a type conversion error during the processing of URIs containing non-ASCII characters, where the parser fails to properly validate index calculations leading to invalid memory access patterns. The issue manifests when malicious servers craft specially formatted URIs that contain international characters or extended ASCII sequences, triggering the problematic code path in the URI parsing logic.
The technical implementation of this vulnerability stems from improper handling of character encoding within the uri_lookup function, which is responsible for parsing and processing Uniform Resource Identifiers. When non-ASCII characters are encountered in a URI, the parser attempts to convert these characters into internal representations while simultaneously calculating array indices for lookup operations. The type conversion error occurs when a 32-bit integer value is improperly cast to a 64-bit context, resulting in negative index values that cause the parser to attempt memory access at invalid addresses. This memory access violation occurs because the array bounds checking mechanism fails to account for the sign extension that occurs during the type conversion process. The vulnerability specifically impacts 64-bit platforms due to the architectural differences in how signed and unsigned integer operations are handled across different processor architectures.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to crash applications that depend on the neon library for HTTP communication. Systems utilizing the affected version of neon for web browsing, file transfer, or web service interactions become vulnerable to remote exploitation, potentially affecting web browsers, download managers, and other applications that make HTTP requests. The denial of service condition is particularly concerning because it can be triggered by simply visiting a malicious website or interacting with a compromised web server, requiring no special privileges or authentication from the attacker. The vulnerability demonstrates a fundamental flaw in input validation and memory management practices, where the parser fails to properly sanitize or validate the input data before performing array operations that assume valid index ranges.
Mitigation strategies for CVE-2007-0157 should focus on immediate version upgrades to neon 0.26.3 or later, which contain the necessary patches to address the type conversion error in the uri_lookup function. Organizations should prioritize updating their systems and applications that rely on the neon library, particularly those handling web content or making HTTP requests to untrusted sources. Additional defensive measures include implementing proper input validation at application layers that utilize the neon library, deploying network-level filtering to block suspicious URI patterns, and monitoring for unusual crash patterns or service disruptions that might indicate exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper validation of array index values, and represents a common pattern in software security flaws related to integer overflows and underflows. From an attack perspective, this vulnerability maps to ATT&CK technique T1499.004 for network denial of service, as it enables attackers to disrupt service availability through carefully crafted input that triggers memory corruption. The patch implementation for this vulnerability typically involves adding proper bounds checking and ensuring that type conversions maintain valid index ranges regardless of the underlying platform architecture, thereby preventing the generation of negative array indices during URI processing operations.