CVE-2026-42507 in net-textproto
Summary
by MITRE • 06/03/2026
When returning errors, functions in the net/textproto package would include its input as part of the error. This might allow an attacker to inject misleading content to errors that are printed or logged.
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Analysis
by VulDB Data Team • 06/04/2026
The vulnerability described relates to improper error handling within the net/textproto package, which is a core component of the go programming language used for handling text-based protocols such as http and smtp. This flaw manifests when functions within the package return error messages that contain portions of the original input data, creating a potential information disclosure and manipulation vector. The technical implementation involves the error generation mechanism that directly incorporates user-supplied input into error strings without proper sanitization or filtering, which violates fundamental security principles of input validation and output encoding. This behavior creates a scenario where malicious actors can craft specific inputs that, when processed by these functions, result in error messages containing unintended content that could be misleading or harmful to system administrators and security monitoring tools.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to manipulate error messages in ways that obscure the true nature of system issues or inject misleading information into logs and monitoring systems. When error messages contain raw input data, they can potentially include sensitive information such as authentication tokens, personal data, or system credentials that were part of the malformed input. This creates a risk for audit trails and incident response activities where error logs serve as crucial forensic evidence. The vulnerability aligns with CWE-20, which addresses improper input validation, and CWE-117, which covers improper output escaping, as the system fails to properly sanitize data before including it in error messages. From an attacker perspective, this represents a low-effort vector for information gathering and potential deception, as demonstrated by ATT&CK technique T1070.004 for Indicator Removal on Host, where attackers might attempt to manipulate error outputs to hide malicious activities or confuse security analysts.
Mitigation strategies for this vulnerability require implementing proper input sanitization and output encoding practices within the net/textproto package and similar components throughout the application stack. Development teams should ensure that error messages are generated using parameterized error strings that do not directly incorporate raw input data, instead using placeholders or sanitized representations of input values. The solution involves modifying the error generation logic to strip or encode potentially problematic content before inclusion in error messages, which aligns with security best practices outlined in OWASP Top 10 and NIST SP 800-53. Organizations should also implement comprehensive logging policies that separate raw input data from error messages and consider implementing input validation layers that reject malformed data before it reaches the error handling components. Regular security code reviews should focus on error handling patterns and ensure that no sensitive data is inadvertently exposed through error messages, particularly in production environments where system logs serve as critical operational and forensic resources.