CVE-2008-5351 in SDKJDK
Summary
by MITRE
Java Runtime Environment (JRE) for Sun JDK and JRE 6 Update 10 and earlier; JDK and JRE 5.0 Update 16 and earlier; and SDK and JRE 1.4.2_18 and earlier accepts UTF-8 encodings that are not the "shortest" form, which makes it easier for attackers to bypass protection mechanisms for other applications that rely on shortest-form UTF-8 encodings.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/21/2019
The vulnerability described in CVE-2008-5351 represents a critical encoding handling flaw within the Java Runtime Environment that affects multiple versions of the JDK and JRE across different major releases. This issue stems from the Java implementation's failure to properly validate UTF-8 encoding sequences, specifically allowing non-conforming encodings that do not adhere to the shortest form specification. The vulnerability exists in versions prior to JDK/JRE 6 Update 10, JDK/JRE 5.0 Update 16, and SDK/JRE 1.4.2_18, creating a widespread impact across legacy Java installations that remain in operational environments.
The technical flaw lies in the Java runtime's UTF-8 decoder implementation which does not enforce the strict shortest-form UTF-8 encoding rules defined in RFC 3629. In standard UTF-8 encoding, each character must be represented using the minimum number of bytes possible, with specific bit patterns that identify the length of the sequence. However, the affected Java versions accept UTF-8 sequences that use longer encodings than necessary, such as representing a single-byte ASCII character using a multi-byte sequence. This behavior creates a discrepancy between how Java processes UTF-8 data and how other applications expect UTF-8 to be formatted, particularly in security-sensitive contexts where encoding validation is crucial.
The operational impact of this vulnerability is significant for applications that depend on UTF-8 encoding validation as part of their security mechanisms. Attackers can exploit this weakness by crafting malicious input that uses non-shortest-form UTF-8 sequences to bypass security filters, access controls, or validation routines that assume standard UTF-8 encoding. This creates opportunities for privilege escalation, data injection attacks, or bypassing input sanitization that relies on proper UTF-8 encoding. The vulnerability particularly affects web applications, file processing systems, and any environment where user input is processed through Java-based components and where UTF-8 encoding is expected to be strictly enforced.
From a cybersecurity perspective, this vulnerability aligns with CWE-176, which specifically addresses issues related to encoding problems in software implementations. The flaw enables techniques that fall under ATT&CK tactic T1059.007 for command and scripting interpreter, and T1133 for external remote services, as attackers can manipulate input encoding to circumvent security controls. The vulnerability's exploitation potential is amplified in environments where Java applications interface with other systems that enforce strict UTF-8 standards, creating a mismatch that attackers can leverage to gain unauthorized access or execute malicious code. Organizations should prioritize patching affected Java installations and implementing additional input validation layers to mitigate the risk of exploitation, particularly in security-sensitive applications where encoding validation is part of the defense-in-depth strategy.