CVE-2026-56852 in Google
Summary
by MITRE • 07/21/2026
A norm.Iter can enter an infinite loop when handling input containing invalid UTF-8 bytes.
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Analysis
by VulDB Data Team • 07/21/2026
The vulnerability described involves a critical flaw in the norm.Iter iterator mechanism that processes input data containing invalid UTF-8 byte sequences. This issue represents a classic example of improper input validation and error handling within text processing libraries, where the system fails to properly terminate iteration when encountering malformed data. The problem manifests specifically when the iterator attempts to parse UTF-8 encoded data that contains invalid byte sequences, causing the control flow to become trapped in an endless loop.
The technical root cause stems from inadequate boundary checking and state management within the iteration logic. When norm.Iter encounters invalid UTF-8 bytes, it fails to properly detect the malformed sequence and instead continues attempting to process what should be considered error conditions. This behavior aligns with CWE-835, which addresses loops that do not contain a valid exit condition or proper termination mechanism. The iterator's internal state management becomes corrupted when processing invalid data, leading to repeated execution of the same iteration steps without advancing through the input stream.
From an operational perspective, this vulnerability presents significant security implications as it can be exploited to cause denial of service attacks against applications relying on the affected library. An attacker could craft malicious input containing carefully constructed invalid UTF-8 sequences that would trigger the infinite loop, consuming system resources and potentially causing application crashes or unresponsiveness. The attack surface extends beyond simple resource exhaustion to include potential system instability when multiple such loops occur simultaneously.
The impact extends to various security frameworks and attack methodologies as outlined in the MITRE ATT&CK framework under the T1499 category for network denial of service attacks. Applications using norm.Iter for text processing, data validation, or input sanitization become vulnerable to these persistent loops that can be triggered through any user-controllable input source, including web forms, file uploads, or network protocols. This vulnerability particularly affects systems where UTF-8 validation is performed in tight loops without proper timeout mechanisms or iteration limits.
Mitigation strategies should include implementing strict bounds checking and maximum iteration limits within the iterator implementation to prevent indefinite execution when encountering invalid sequences. Additionally, applications should employ input sanitization routines that validate UTF-8 encoding before processing with norm.Iter, and implement timeout mechanisms for text processing operations. The fix should ensure proper error handling that terminates iteration upon detection of invalid UTF-8 bytes rather than allowing the loop to continue indefinitely. Security-conscious development practices should enforce defensive programming techniques including maximum iteration counters and early termination conditions for all iterative text processing functions, aligning with secure coding guidelines from organizations like OWASP and NIST.