CVE-2024-30949: Newlib_project Newlib RCE Vulnerability

CVE-2024-30949 Overview

CVE-2024-30949 is a critical vulnerability affecting the Newlib C library version 4.3.0. The vulnerability exists in the _gettimeofday function where improper time unit scaling can lead to an integer overflow condition, ultimately enabling an attacker to execute arbitrary code. Newlib is a widely-used C library implementation designed for embedded systems, making this vulnerability particularly concerning for IoT devices, firmware, and other resource-constrained environments.

Critical Impact

This vulnerability allows remote attackers to execute arbitrary code without requiring authentication or user interaction. The flaw in time unit scaling within _gettimeofday can be exploited over the network, potentially compromising embedded systems and IoT devices running affected versions of Newlib.

Affected Products

• Newlib v.4.3.0
• Applications and embedded systems compiled with Newlib 4.3.0
• Firmware implementations utilizing the vulnerable _gettimeofday function

Discovery Timeline

• 2024-08-20 - CVE-2024-30949 published to NVD
• 2024-08-21 - Last updated in NVD database

Technical Details for CVE-2024-30949

Vulnerability Analysis

This vulnerability stems from improper handling of time unit conversions within the _gettimeofday function in Newlib. The function performs arithmetic operations on time values that can overflow when processing certain inputs, leading to memory corruption. The vulnerability is classified under CWE-190 (Integer Overflow or Wraparound) and CWE-787 (Out-of-bounds Write), indicating that the integer overflow subsequently enables writing data beyond allocated buffer boundaries.

The _gettimeofday function is commonly used to retrieve the current time in embedded applications. When the time unit scaling logic receives specially crafted input values, the arithmetic operations can cause the integer value to wrap around, resulting in an unexpectedly small buffer allocation or incorrect memory offset calculation. This creates conditions where an attacker can write arbitrary data to memory locations outside the intended boundaries.

Root Cause

The root cause of CVE-2024-30949 lies in insufficient bounds checking during time unit scaling operations within the _gettimeofday implementation. When converting between time units (such as seconds to microseconds), the multiplication operations can exceed the maximum value representable by the integer type, causing an overflow. This overflow then propagates to subsequent memory operations, creating an exploitable out-of-bounds write condition.

Attack Vector

The vulnerability can be exploited remotely over a network without requiring authentication or user interaction. An attacker can craft malicious input that triggers the integer overflow during time unit calculations. Since the _gettimeofday function may be invoked in network-facing code paths, particularly in embedded systems handling time synchronization or logging operations, remote exploitation is feasible.

The attack flow involves:

1. Identifying a target system using Newlib 4.3.0
2. Sending crafted input that reaches the _gettimeofday function
3. Triggering the integer overflow during time unit scaling
4. Leveraging the resulting out-of-bounds write for code execution

The vulnerability mechanism involves time unit scaling overflow in the _gettimeofday function. When time values undergo conversion operations, improper handling of large values causes integer overflow, which subsequently corrupts memory through out-of-bounds write operations. For detailed technical analysis, refer to the GitHub Gist PoC and the Sourceware mailing list patch discussion.

Detection Methods for CVE-2024-30949

Indicators of Compromise

• Unexpected crashes or segmentation faults in applications using _gettimeofday
• Anomalous memory access patterns in embedded system logs
• Core dumps showing corruption near time-related data structures
• Unusual network traffic targeting time synchronization endpoints

Detection Strategies

• Implement runtime memory safety checks using tools like AddressSanitizer (ASan) during development and testing
• Monitor for integer overflow conditions in time-handling code paths
• Deploy intrusion detection rules that identify exploitation attempts targeting time-related functions
• Audit application binaries to identify linking against vulnerable Newlib 4.3.0

Monitoring Recommendations

• Enable verbose logging for time-related system calls in embedded applications
• Implement anomaly detection for unexpected behavior in _gettimeofday invocations
• Monitor memory allocation patterns for inconsistencies indicative of overflow exploitation
• Set up alerts for crash reports involving time-handling functions

How to Mitigate CVE-2024-30949

Immediate Actions Required

• Identify all systems and applications compiled with Newlib 4.3.0
• Prioritize patching embedded systems and IoT devices using the vulnerable library
• Apply available patches from the Newlib project or recompile applications with updated library versions
• Implement network segmentation to limit exposure of vulnerable embedded systems

Patch Information

A patch has been developed and submitted to the Newlib project. The fix addresses the integer overflow by implementing proper bounds checking before time unit scaling operations. Organizations should update to a patched version of Newlib or apply the commit referenced in the Newlib Cygwin repository.

The patch details were submitted to the Sourceware mailing list and should be incorporated into future Newlib releases.

Workarounds

• Implement input validation before calling _gettimeofday to prevent overflow-inducing values
• Use alternative time retrieval mechanisms that include overflow protection
• Deploy network-level filtering to block potentially malicious traffic targeting vulnerable systems
• Consider wrapping _gettimeofday calls with bounds-checking logic in application code

# Verification example - Check Newlib version in compiled binary
strings /path/to/binary | grep -i "newlib"
# Look for version strings indicating 4.3.0

# Identify affected binaries using ldd or nm
nm /path/to/binary | grep _gettimeofday