CVE-2017-18212 in JerryScript
Summary
by MITRE
An issue was discovered in JerryScript 1.0. There is a heap-based buffer over-read in the lit_read_code_unit_from_hex frunction in lit/lit-char-helpers.c via a RegExp("[\x0"); payload.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 02/16/2023
The vulnerability identified as CVE-2017-18212 represents a critical heap-based buffer over-read flaw within JerryScript version 1.0, a lightweight javascript engine designed for resource-constrained embedded systems. This issue manifests in the lit_read_code_unit_from_hex function located within the lit/lit-char-helpers.c source file, demonstrating how seemingly benign input processing can lead to severe memory corruption vulnerabilities. The vulnerability specifically triggers when processing regular expression patterns containing malformed hexadecimal sequences, creating a scenario where the engine reads beyond allocated memory boundaries.
The technical exploitation of this vulnerability occurs through a carefully crafted RegExp payload that includes a null character within a hexadecimal escape sequence. When JerryScript attempts to parse this malformed input, the lit_read_code_unit_from_hex function fails to properly validate the bounds of the character buffer, allowing an attacker to read memory locations that should remain inaccessible. This over-read condition can potentially expose sensitive data from adjacent memory regions, including stack contents, heap metadata, or other critical program information. The vulnerability falls under CWE-125, which specifically addresses out-of-bounds read conditions, and represents a classic example of insufficient boundary checking in string processing functions.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially enable more sophisticated attacks such as remote code execution or denial of service conditions. Attackers leveraging this vulnerability could exploit the memory corruption to manipulate program flow, particularly in embedded systems where JerryScript is commonly deployed for web-based interfaces or IoT applications. The vulnerability's exploitation requires minimal input complexity, making it particularly dangerous as it can be triggered through standard javascript execution paths without requiring special privileges or complex attack vectors.
Security practitioners should prioritize this vulnerability for remediation given its potential for remote exploitation in environments where JerryScript processes untrusted input. The recommended mitigation strategy involves upgrading to JerryScript version 2.0 or later, where the buffer over-read issue has been addressed through proper bounds checking and input validation. Additionally, implementing strict input sanitization for regular expression patterns and monitoring for unusual memory access patterns can provide defensive measures against potential exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.007 for scripting languages, highlighting the importance of validating and sanitizing all input processed by scripting engines in embedded environments.