CVE-2026-3579: wolfSSL Information Disclosure Vulnerability

CVE-2026-3579 Overview

CVE-2026-3579 is a timing side-channel vulnerability affecting wolfSSL version 5.8.4 on RISC-V RV32I architectures. The vulnerability stems from the lack of a constant-time software implementation for 64-bit multiplication operations. When compiled for RISC-V RV32I platforms, the compiler-inserted __muldi3 subroutine executes in variable time based on operand values, creating a timing side-channel that may expose sensitive cryptographic data.

This vulnerability affects multiple SP (Single Precision) math functions including sp_256_mul_9, sp_256_sqr_9, and related cryptographic operations. Attackers capable of measuring precise timing variations could potentially extract sensitive key material through statistical analysis of execution times.

Critical Impact

Timing variations in cryptographic multiplication operations may allow local attackers to extract sensitive key material through side-channel analysis on RISC-V RV32I embedded systems.

Affected Products

• wolfSSL 5.8.4 on RISC-V RV32I architectures
• Systems using SP math functions (sp_256_mul_9, sp_256_sqr_9, etc.) on affected platforms
• Embedded devices and IoT systems utilizing wolfSSL on 32-bit RISC-V processors

Discovery Timeline

• 2026-03-19 - CVE CVE-2026-3579 published to NVD
• 2026-03-19 - Last updated in NVD database

Technical Details for CVE-2026-3579

Vulnerability Analysis

This vulnerability falls under CWE-203 (Observable Discrepancy), a category of timing side-channel attacks where an attacker can extract information based on observable differences in system behavior. The core issue lies in the non-constant-time execution of multiplication operations when wolfSSL is compiled for RISC-V RV32I architectures.

On 32-bit RISC-V platforms lacking native 64-bit multiplication instructions, the compiler automatically inserts the __muldi3 subroutine to handle 64-bit multiplications. This software emulation routine does not execute in constant time—its execution duration varies depending on the operand values being processed. When these operations involve cryptographic key material, the timing variations create a measurable side-channel.

The attack requires local access to the target system and the ability to perform precise timing measurements. While the attack complexity is high, successful exploitation could lead to partial disclosure of cryptographic secrets, making this particularly concerning for embedded systems and IoT devices where physical access may be more feasible.

Root Cause

The root cause is the absence of constant-time multiplication implementations in the wolfSSL SP math library when targeting RISC-V RV32I architectures. The affected functions (sp_256_mul_9, sp_256_sqr_9, and others) rely on the compiler's built-in __muldi3 helper function for 64-bit multiplication on 32-bit platforms.

The __muldi3 subroutine, provided by the compiler runtime library (such as libgcc), was not designed with cryptographic security in mind. Its execution time correlates with the values of the input operands, particularly when handling leading zeros or specific bit patterns. This data-dependent timing behavior violates the constant-time requirement essential for cryptographic implementations to resist side-channel attacks.

Attack Vector

The attack vector is local, requiring an attacker to have the ability to execute code on the same system or to measure timing variations through other means such as electromagnetic emanations or power analysis. The attack methodology typically involves:

1. Timing Measurement: The attacker repeatedly triggers cryptographic operations involving the vulnerable multiplication functions while measuring execution time with high precision.

2. Statistical Analysis: By collecting numerous timing samples across different operations, the attacker can correlate timing variations with specific bit patterns in the secret key material.

3. Key Recovery: Through techniques such as differential timing analysis, the attacker progressively recovers portions of the private key by identifying which operand values cause faster or slower execution.

The vulnerability primarily affects elliptic curve cryptography operations on P-256 curves, where the sp_256_mul_9 and sp_256_sqr_9 functions are used in scalar multiplication operations that process private key bits.

Detection Methods for CVE-2026-3579

Indicators of Compromise

• Unusual patterns of repeated cryptographic operations from suspicious processes
• High-frequency timing measurement attempts or access to high-resolution timers
• Abnormal process behavior involving repeated TLS handshakes or cryptographic key operations
• Evidence of timing analysis tools or statistical collection frameworks on the system

Detection Strategies

• Monitor for processes making excessive calls to wolfSSL cryptographic functions in short time periods
• Implement anomaly detection for unusual access patterns to cryptographic APIs
• Deploy application-level logging to track frequency and patterns of TLS/cryptographic operations
• Review compiled binaries on RISC-V RV32I systems for presence of __muldi3 calls in cryptographic code paths

Monitoring Recommendations

• Enable detailed logging for wolfSSL library operations in production environments
• Implement runtime performance monitoring to detect timing measurement attempts
• Monitor system calls related to high-resolution timing (clock_gettime, rdcycle on RISC-V)
• Deploy host-based intrusion detection to identify potential side-channel attack tools

How to Mitigate CVE-2026-3579

Immediate Actions Required

• Identify all systems using wolfSSL 5.8.4 on RISC-V RV32I architectures
• Evaluate the risk exposure based on physical access controls and deployment environment
• Apply the patch from the official wolfSSL repository when available
• Consider migrating affected workloads to platforms with constant-time multiplication support

Patch Information

The wolfSSL development team has addressed this vulnerability through a pull request that introduces constant-time multiplication implementations for RISC-V RV32I platforms. The fix ensures that SP math functions no longer rely on the compiler's variable-time __muldi3 subroutine for cryptographic operations.

For patch details and updates, refer to the GitHub Pull Request for wolfSSL.

Organizations should update to the patched version of wolfSSL as soon as it becomes available through official channels. Until the patch is applied, consider the following workarounds.

Workarounds

• Limit physical access to affected embedded systems and IoT devices
• Disable or restrict access to high-resolution timing mechanisms where feasible
• Consider using alternative cryptographic libraries with verified constant-time implementations for critical operations
• Implement additional access controls to prevent unauthorized code execution on affected systems
• Evaluate using hardware acceleration if available on the target RISC-V platform to bypass software multiplication