Overview
CVE-2025-11934 describes an improper input validation vulnerability found in wolfSSL versions 5.8.2 and earlier. This flaw resides in the TLS 1.3 CertificateVerify signature algorithm negotiation process. The vulnerability allows a malicious server to potentially downgrade the signature algorithm used for TLS connections, potentially weakening the security of the connection. This can occur if the server improperly negotiates a weaker signature algorithm than initially proposed by the client, even if the client supports the downgraded algorithm.
Technical Details
The vulnerability stems from inadequate validation during the signature algorithm negotiation phase of the TLS 1.3 handshake. Specifically, when a client advertises support for a preferred signature algorithm (e.g., ECDSA P-521), the server could respond with a less secure option (e.g., ECDSA P-256), even if the client supports the less secure algorithm. The wolfSSL implementation prior to the fix did not properly enforce that the chosen signature algorithm aligns with the client’s original preference within the bounds of what the client also supports. This weakness could then allow an attacker to force the use of weaker cryptographic primitives, increasing the possibility of successful cryptanalytic attacks.
CVSS Analysis
The CVSS score for CVE-2025-11934 is currently unavailable (N/A). The severity is also currently marked as N/A. However, it’s crucial to understand the potential impact, which could be significant depending on the specific implementation and context. Further analysis is needed to assign accurate CVSS metrics, considering factors like attack complexity, scope, and confidentiality impact.
Possible Impact
The primary impact of a successful signature algorithm downgrade is a potential weakening of the cryptographic protection afforded to the TLS connection. This could lead to:
- Increased susceptibility to man-in-the-middle (MitM) attacks: Weaker signature algorithms may be easier to break, allowing an attacker to intercept and modify communications between the client and server.
- Compromised confidentiality: If the signature algorithm is successfully compromised, the attacker could potentially decrypt sensitive data transmitted over the connection.
- Integrity breaches: An attacker could alter data in transit without detection.
Mitigation and Patch Steps
The primary mitigation is to upgrade to a patched version of wolfSSL that addresses this vulnerability. Specifically, upgrade to a version later than 5.8.2. According to the available information, the fix has been implemented in the wolfSSL project.
- Upgrade wolfSSL: The most effective mitigation is to upgrade to the latest stable version of wolfSSL.
- Verify TLS Configuration: Ensure your TLS configuration adheres to security best practices and that your server does not negotiate weaker algorithms unless absolutely necessary for compatibility reasons.
- Monitor Network Traffic: Implement network monitoring to detect any attempts to downgrade TLS connections.
References
wolfSSL GitHub Repository
wolfSSL Pull Request #9113 (Fix for CVE-2025-11934)
