Overview
CVE-2025-11932 identifies a potential vulnerability within the WolfSSL library related to the verification of the TLS 1.3 Pre-Shared Key (PSK) binder. The issue stems from the server’s prior use of a non-constant time method for PSK binder verification. This could potentially expose information about the PSK binder to attackers, potentially compromising the security of TLS 1.3 connections.
Technical Details
The vulnerability arises because the time taken to verify the PSK binder depends on the content of the binder itself when using a non-constant time algorithm. This timing difference, even if minuscule, can be measured by an attacker through carefully crafted requests and statistical analysis. This attack, known as a timing attack, allows an attacker to potentially deduce parts of the PSK binder, effectively weakening the encryption.
Specifically, the vulnerability resided in the way the WolfSSL library compared the received PSK binder with the expected value. By using a non-constant time comparison algorithm, the execution time varied depending on the first differing byte. Modern CPUs and network environments can make these timing differences difficult to exploit, but they are still present.
The fix involves replacing the vulnerable code with a constant-time equivalent, ensuring the comparison takes the same amount of time regardless of the input data. This effectively eliminates the timing side channel.
CVSS Analysis
As of the publication of this analysis, CVE-2025-11932 has a CVSS score of N/A. This is likely because the practical exploitability of this vulnerability can be difficult depending on network latency, CPU architecture, and other factors. A successful attack requires very precise timing measurements, making it challenging to execute in real-world scenarios. The severity is also N/A. It is crucial to note that while the CVSS score might be absent or low, this does not negate the potential risk, especially in highly sensitive environments. System administrators and developers should evaluate their specific context to determine the level of concern.
Possible Impact
While the difficulty of exploitation might be high, the potential impact of successfully exploiting CVE-2025-11932 could be significant. A successful attack could lead to:
- Compromise of TLS 1.3 encrypted sessions.
- Exposure of sensitive data transmitted over the compromised connections.
- Potential for man-in-the-middle attacks.
The impact is more pronounced in systems where performance is prioritized, and timing variations might be more easily observed. Also, embedded systems with limited resources might be more vulnerable due to less noise in the timing measurements.
Mitigation and Patch Steps
The recommended mitigation is to update WolfSSL to a version containing the fix for this vulnerability. According to the provided reference, the fix is included in the pull request. Users should consult the WolfSSL release notes for specific version information.
Steps to mitigate the vulnerability:
- Identify systems using the affected WolfSSL library.
- Determine the current version of WolfSSL in use.
- Upgrade to the patched version of WolfSSL as specified by the vendor.
- Recompile and redeploy applications using the updated library.
- Test the updated systems to ensure proper functionality and security.
References
- CVE ID: CVE-2025-11932
- WolfSSL Pull Request: wolfSSL/wolfssl#9223
