CVE-2023-23950 in Symantec Identity Manager
Summary
by MITRE • 01/26/2023
User’s supplied input (usually a CRLF sequence) can be used to split a returning response into two responses.
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Analysis
by VulDB Data Team • 10/15/2025
This vulnerability represents a critical HTTP response splitting flaw that allows attackers to manipulate server responses by injecting carriage return line feed sequences into user-supplied input. The issue manifests when applications fail to properly sanitize or validate input data before incorporating it into HTTP response headers or body content. When such input contains CRLF sequences, these characters can be interpreted by the HTTP protocol as delimiters that separate one response from another, enabling malicious actors to inject additional HTTP responses into the server's output stream.
The technical exploitation of this vulnerability occurs through the manipulation of HTTP response headers where user-controllable data is directly concatenated without proper sanitization. When an attacker provides input containing characters like \r\n or %0d%0a, these sequences can cause the web server to interpret the injected data as the end of the initial response header and begin a new response. This creates a scenario where the server sends multiple responses to a single request, potentially allowing attackers to inject malicious content, perform session hijacking, or redirect users to malicious websites. The vulnerability is particularly dangerous because it can be leveraged to bypass security controls, inject cross-site scripting payloads, or manipulate application behavior in ways that compromise the integrity of the HTTP communication channel.
The operational impact of this vulnerability extends beyond simple data corruption, as it can enable sophisticated attacks such as cache poisoning, session fixation, and cross-site request forgery exploitation. Attackers can use response splitting to inject malicious content into the response stream, potentially redirecting users to phishing sites or injecting malicious scripts that persist in the user's browser cache. This vulnerability directly maps to CWE-113, which describes improper neutralization of CRLF sequences in HTTP headers, and aligns with ATT&CK technique T1584.001 for the development of capabilities to manipulate network traffic. The vulnerability affects web applications that do not properly validate or sanitize user input before using it in HTTP response construction, particularly those handling form submissions, URL parameters, or cookie values.
Mitigation strategies for this vulnerability require comprehensive input validation and sanitization mechanisms that strip or encode CRLF sequences from user-supplied data before processing. Organizations should implement strict validation of all HTTP response headers and ensure that user input is properly escaped or encoded to prevent interpretation as protocol delimiters. The implementation of secure coding practices including the use of parameterized inputs, proper header validation, and response sanitization routines can effectively prevent exploitation. Additionally, web application firewalls and security proxies should be configured to detect and block CRLF injection attempts, while regular security testing including penetration testing and code review processes should be conducted to identify and remediate similar vulnerabilities. Organizations should also consider implementing Content Security Policy headers and other security measures that can help mitigate the impact of successful exploitation attempts.