CVE-2026-102521 in lib0
Summary
by MITRE • 09/29/2026
The decoder in `readFromDataView` in lib0 before 0.2.119 can be tricked into reading more than it should from a buffer. The vulnerability allows reading past the decoders' view, thus exposing adjacent process memory. This can be anything that is currently in the head, for example credentials or logs. This is similar to but different from GHSA-r5c8-rf4w-qrq8.
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability identified within lib0 prior to version 0.2.119 represents a critical out-of-bounds read condition located in the `readFromDataView` function. This component is responsible for parsing binary data structures, typically used in collaborative editing protocols or similar applications that rely on efficient buffer manipulation. The core technical flaw stems from an insufficient validation of boundary conditions during the decoding process. Specifically, when processing a DataView object, the decoder fails to correctly verify whether the requested read operation exceeds the allocated length of the underlying buffer. This logical error allows the execution flow to proceed with memory access operations that target addresses beyond the intended scope of the data view.
From an operational perspective, this flaw results in an arbitrary out-of-bounds read, which is classified under CWE-125: Out-of-bounds Read. By reading past the decoders' designated view boundary, the application inadvertently exposes adjacent process memory contents to the attacker or untrusted input source. The data retrieved from these unauthorized memory locations can vary significantly depending on what resides in the immediate vicinity of the buffer at runtime. In practical exploitation scenarios, this could lead to the leakage of sensitive information such as authentication credentials, session tokens, private keys, or internal application logs that happen to be stored in adjacent heap allocations. This type of vulnerability is particularly dangerous because it can facilitate further attacks by providing attackers with the necessary context to bypass security controls or escalate privileges within the affected system.
The nature of this vulnerability shares similarities with previously reported issues such as GHSA-r5c8-rf4w-qrq8, yet it differs in its specific trigger mechanism and the exact memory access pattern exploited. While both involve improper boundary checks in decoding routines, this instance specifically targets the `readFromDataView` method's handling of length parameters relative to the DataView object itself rather than a broader structural parsing error. This distinction is important for developers attempting to patch similar codebases, as it highlights that even well-established libraries can contain subtle edge-case errors when dealing with low-level memory access operations in JavaScript environments like Node.js or modern browsers.
To mitigate this vulnerability, organizations and developers must immediately upgrade lib0 to version 0.2.119 or later, where the boundary checks have been corrected to ensure that read operations do not exceed the allocated buffer limits. For systems unable to update immediately due to dependency constraints, implementing strict input validation at the application layer can provide a temporary defense-in-depth measure. This involves ensuring that all incoming data structures are validated against expected sizes before being passed to the decoder functions. Additionally, enabling memory protection features such as Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP) can help mitigate the impact of information disclosure by making it more difficult for attackers to predict or utilize leaked memory addresses effectively. Monitoring logs for unusual patterns in data parsing errors may also aid in detecting potential exploitation attempts in real-time, aligning with ATT&CK techniques related to Collection via Input Capture and potentially T1059 if used as part of a broader attack chain involving command execution after information gathering.