CVE-2017-1556 in API Connect
Summary
by MITRE
IBM API Connect 5.0.7.0 through 5.0.7.2 is vulnerable to a regular expression attack that could allow an authenticated attacker to use a regex and cause the system to slow or hang. IBM X-Force ID: 131546.
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Analysis
by VulDB Data Team • 01/12/2021
The vulnerability identified as CVE-2017-1556 affects IBM API Connect versions 5.0.7.0 through 5.0.7.2, representing a significant security flaw that could be exploited by authenticated attackers to disrupt system operations. This vulnerability falls under the category of regular expression denial of service attacks, where malicious input patterns can cause the system to consume excessive computational resources and potentially hang or become unresponsive. The issue stems from insufficient input validation and improper handling of regular expression patterns within the API Connect framework, creating a pathway for attackers to craft specific regex expressions that trigger inefficient pattern matching algorithms. The vulnerability is particularly concerning as it requires only authenticated access, meaning that an attacker with valid credentials could exploit this weakness to cause service disruption. This type of attack directly impacts the availability and performance characteristics of the API management platform, potentially affecting thousands of API calls and service integrations that rely on the system's stability.
The technical flaw manifests when the system processes user-supplied regular expressions within API definitions, policy configurations, or request/response validation rules. The underlying implementation does not properly sanitize or limit the complexity of regex patterns, allowing attackers to submit crafted expressions that cause exponential backtracking in the regex engine. This behavior creates a denial of service condition where the system's CPU utilization spikes dramatically and response times become excessive, effectively rendering the service unavailable to legitimate users. The vulnerability is classified as a CWE-400 weakness, specifically related to uncontrolled resource consumption through regular expression complexity. Attackers can leverage this by submitting regex patterns that contain nested quantifiers or backtracking constructs that cause the engine to explore an exponential number of possible matches. The impact extends beyond simple performance degradation to potentially causing complete system hangs, requiring manual intervention to restore normal operations and impacting business continuity.
The operational impact of this vulnerability is substantial for organizations relying on IBM API Connect for their API management needs. Service disruptions caused by this vulnerability can affect multiple concurrent users and applications that depend on the API gateway, leading to cascading failures throughout integrated systems. The authenticated nature of the attack means that insider threats or compromised accounts could be particularly damaging, as the attacker would not need to perform initial reconnaissance or credential acquisition. Organizations may experience extended downtime while system administrators investigate and resolve the issue, potentially leading to revenue loss and customer dissatisfaction. The vulnerability also creates challenges for incident response teams who must differentiate between legitimate high-complexity regex patterns and malicious inputs. From a compliance perspective, this vulnerability could result in violations of service level agreements and regulatory requirements for system availability. The attack vector aligns with ATT&CK technique T1499.004, which involves resource hijacking through denial of service attacks, making it a critical concern for organizations following cybersecurity frameworks that emphasize availability and resilience.
Mitigation strategies for this vulnerability include implementing input validation and sanitization for all user-supplied regular expressions within the API Connect environment, limiting the complexity of regex patterns that can be submitted, and monitoring system performance for unusual resource consumption patterns. Organizations should upgrade to IBM API Connect versions that contain patches addressing this vulnerability, as IBM has released fixes to resolve the regex processing issues. Network segmentation and access controls can help limit the impact if an attacker gains authenticated access, while monitoring systems should be configured to detect and alert on suspicious regex patterns or performance anomalies. The implementation of rate limiting and resource quotas for regex processing can prevent a single malicious input from consuming excessive system resources. Security teams should also consider implementing automated testing of regex patterns during API deployment to identify potentially problematic expressions before they can be exploited. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other components of the API management infrastructure. Additionally, maintaining detailed logs of regex usage and system performance metrics enables better incident response and helps establish baselines for detecting anomalous behavior patterns.