CVE-2025-52471: Espressif ESP-IDF RCE Vulnerability

CVE-2025-52471 Overview

An integer underflow vulnerability has been identified in the ESP-NOW protocol implementation within the ESP Wi-Fi component of Espressif's ESP-IDF (Internet of Things Development Framework). This vulnerability stems from insufficient validation of user-supplied data length in the packet receive function. Under certain conditions, this may lead to out-of-bounds memory access and may allow arbitrary memory write operations. On systems without a memory protection scheme, this behavior could potentially be exploited to achieve remote code execution (RCE) on the target device.

Critical Impact

This integer underflow vulnerability in the ESP-NOW protocol can lead to out-of-bounds memory access and arbitrary memory writes, potentially enabling remote code execution on unprotected IoT devices.

Affected Products

• Espressif ESP-IDF version 5.4.1
• Espressif ESP-IDF version 5.3.3
• Espressif ESP-IDF version 5.2.5
• Espressif ESP-IDF version 5.1.6

Discovery Timeline

• June 24, 2025 - CVE-2025-52471 published to NVD
• January 22, 2026 - Last updated in NVD database

Technical Details for CVE-2025-52471

Vulnerability Analysis

The vulnerability exists in the ESP-NOW protocol implementation, specifically in how the framework processes incoming packet data. ESP-NOW is a connectionless communication protocol developed by Espressif that enables quick and direct communication between ESP devices without requiring a traditional Wi-Fi connection or router.

The core issue involves insufficient validation of the data_len parameter received during packet reception. When a maliciously crafted packet with a manipulated length value is processed, the insufficient bounds checking can cause an integer underflow condition. This occurs when arithmetic operations on the length value produce a negative result that wraps around to a large positive number when interpreted as an unsigned integer.

The consequences of this vulnerability are particularly severe on embedded IoT devices that typically lack memory protection mechanisms such as Address Space Layout Randomization (ASLR) or stack canaries. On such systems, the ability to write arbitrary data to memory locations can be leveraged to overwrite critical program data or inject malicious code.

Root Cause

The root cause of this vulnerability is classified as CWE-191 (Integer Underflow). The ESP-NOW packet receive function fails to properly validate that the user-supplied data_len parameter is a positive value before performing arithmetic operations on it. When negative value calculations occur due to malformed input, the resulting integer underflow can cause the application to access memory outside the intended boundaries.

The vulnerable code path exists in the RX callback mechanism registered via esp_now_register_recv_cb(). Without proper validation, attackers can craft packets that cause the length calculation to underflow, resulting in memory corruption.

Attack Vector

The attack vector for this vulnerability is network-based, requiring the attacker to be within Wi-Fi range of the target ESP device. The ESP-NOW protocol operates on the data link layer and does not require authentication by default, making it accessible to any device within radio range.

An attacker can exploit this vulnerability by:

1. Positioning within Wi-Fi range of a vulnerable ESP device
2. Crafting a malicious ESP-NOW packet with a manipulated data length field designed to trigger the integer underflow
3. Transmitting the packet to the target device
4. Exploiting the resulting out-of-bounds memory access to achieve arbitrary memory writes
5. On devices without memory protection, leveraging the memory corruption to execute arbitrary code

The vulnerability requires no user interaction and no prior authentication, making it particularly dangerous for deployed IoT devices in accessible locations.

Detection Methods for CVE-2025-52471

Indicators of Compromise

• Unexpected device reboots or crashes in ESP-based IoT devices, particularly those using ESP-NOW communication
• Anomalous Wi-Fi traffic patterns with malformed ESP-NOW frames detected on the network
• Device firmware behaving unexpectedly or executing unauthorized commands

Detection Strategies

• Monitor ESP device logs for memory corruption errors, segmentation faults, or watchdog timer resets
• Implement network monitoring to detect anomalous ESP-NOW frame sizes or patterns that deviate from normal protocol specifications
• Deploy wireless intrusion detection systems capable of analyzing 802.11 action frames used by ESP-NOW

Monitoring Recommendations

• Enable verbose logging on ESP devices during development and testing to identify potential exploitation attempts
• Implement firmware integrity verification mechanisms to detect unauthorized modifications resulting from successful exploitation
• Monitor device behavior metrics such as memory usage, CPU utilization, and communication patterns for anomalies

How to Mitigate CVE-2025-52471

Immediate Actions Required

• Upgrade to patched ESP-IDF versions: 5.4.2, 5.3.4, 5.2.6, or the updated 5.1.6 release
• For ESP-IDF v5.3 and earlier, implement the application-level workaround by validating that the data_len parameter received in the RX callback is a positive value before further processing
• Audit deployed IoT devices to identify those running vulnerable ESP-IDF versions

Patch Information

Espressif has released patches addressing this vulnerability across multiple ESP-IDF branches. The fixes add comprehensive validation logic on user-supplied data length during packet reception to prevent integer underflow caused by negative value calculations.

Relevant security patches are available through the following commits:

• Espressif Commit Update
• Espressif Commit Fix
• Espressif Commit Enhancement
• Espressif Commit Change
• Espressif Commit Improvement
• Espressif Commit Bugfix

For complete details, refer to the Espressif Security Advisory.

Workarounds

• For ESP-IDF v5.3 and earlier: Add validation in your application code to check that the data_len parameter received in the RX callback (registered via esp_now_register_recv_cb()) is a positive value before any further processing
• For ESP-IDF v5.4 and later: No application-level workaround is available; upgrading to a patched version is required
• Consider implementing additional network segmentation to limit exposure of vulnerable IoT devices until patches can be applied

// Workaround for ESP-IDF v5.3 and earlier
// Add this validation in your ESP-NOW receive callback

void esp_now_recv_cb(const uint8_t *mac_addr, const uint8_t *data, int data_len) {
    // Validate data_len is positive before processing
    if (data_len <= 0) {
        // Reject packets with invalid length
        return;
    }
    
    // Continue with normal packet processing
    // ...
}