CVE-2024-27280 in StringIO
Summary
by MITRE • 05/14/2024
A buffer-overread issue was discovered in StringIO 3.0.1, as distributed in Ruby 3.0.x through 3.0.6 and 3.1.x through 3.1.4. The ungetbyte and ungetc methods on a StringIO can read past the end of a string, and a subsequent call to StringIO.gets may return the memory value. 3.0.3 is the main fixed version; however, for Ruby 3.0 users, a fixed version is stringio 3.0.1.1, and for Ruby 3.1 users, a fixed version is stringio 3.0.1.2.
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Analysis
by VulDB Data Team • 05/03/2025
The buffer-overread vulnerability in StringIO 3.0.1 represents a critical memory safety issue that affects Ruby implementations across multiple versions. This flaw specifically targets the ungetbyte and ungetc methods within the StringIO class, which are designed to allow data to be pushed back onto a stream for subsequent reading operations. The vulnerability manifests when these methods attempt to read past the boundaries of the underlying string buffer, creating a condition where memory locations beyond the intended data structure are accessed. This behavior fundamentally violates the principle of bounded buffer access that is essential for preventing memory corruption and potential exploitation.
The technical implementation of this vulnerability stems from inadequate bounds checking within the StringIO implementation. When ungetbyte and ungetc methods are invoked, they manipulate internal buffer pointers without proper validation of the buffer limits. This allows attackers to cause the methods to access memory locations that extend beyond the allocated string buffer, potentially reading sensitive data from adjacent memory regions. The subsequent call to StringIO.gets method then returns this read memory content, which can contain arbitrary data from the process memory space including potentially sensitive information, stack contents, or heap data. This particular flaw aligns with CWE-129, which describes improper validation of buffer limits, and represents a classic example of unsafe memory access patterns that can lead to information disclosure or further exploitation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to potentially extract sensitive data from memory locations that should remain protected. When applications utilize StringIO for processing user input or handling data streams, particularly in web applications or systems that process untrusted data, the vulnerability creates a potential attack surface where memory contents can be accessed and potentially exfiltrated. The vulnerability is particularly concerning in environments where Ruby applications handle sensitive data processing, as the memory overread could expose database credentials, session tokens, cryptographic keys, or other confidential information that resides in adjacent memory locations. This type of vulnerability maps to ATT&CK technique T1005 which involves data from local system collection, and can potentially lead to broader compromise through information gathering.
Mitigation strategies for this vulnerability require immediate patching of affected Ruby installations through the specified fixed versions. Ruby 3.0 users must upgrade to stringio 3.0.1.1 or Ruby 3.0.3, while Ruby 3.1 users should upgrade to stringio 3.0.1.2 or Ruby 3.1.4. Organizations should prioritize this update across all affected systems and conduct thorough testing to ensure compatibility with existing applications. Additionally, developers should implement defensive programming practices such as validating input data before processing and avoiding reliance on potentially vulnerable methods when handling sensitive data streams. The vulnerability highlights the importance of proper buffer management and bounds checking in memory-safe programming practices, particularly in interpreted languages where such protections may not be as rigorously enforced as in compiled languages. Security monitoring should include detection of unusual memory access patterns and potential information disclosure attempts that could indicate exploitation of this vulnerability.