CVE-2025-59432: Timing Attack Vulnerability in SCRAM Authentication

Introduction

A new vulnerability, CVE-2025-59432, has been identified in the SCRAM (Salted Challenge Response Authentication Mechanism) implementation within the Java library com.ongres.scram:scram-common. This flaw exposes applications using this component to timing attacks, potentially allowing attackers to infer sensitive authentication secrets.

This blog explains the technical root cause, how it was fixed, and what developers and security engineers should do to mitigate the risk.

Key Takeaways

• The issue arises from non-constant-time comparisons in cryptographic validation.
• Attackers can exploit timing differences to infer secret values used in authentication.
• The fix replaces Arrays.equals() with MessageDigest.isEqual(), ensuring constant-time comparisons.

What is SCRAM Authentication and Why Does It Matter?

SCRAM (Salted Challenge Response Authentication Mechanism) is used in protocols like SASL to authenticate clients securely without transmitting plaintext passwords. The Java library com.ongres.scram:scram-common handles crucial operations like generating client proofs and server signatures.

However, a small coding oversight in how secrets are compared during these operations led to a major timing side-channel vulnerability.

What is a Timing Attack and Why is It Dangerous?

A timing attack is a form of side-channel attack where an adversary measures how long an operation takes to execute. If the execution time varies based on the data being processed (like password bytes), an attacker can infer partial information about secret values.

In this case, the vulnerable code used java.util.Arrays.equals(byte[], byte[]) for comparing secret byte arrays. This method exits early when a mismatch is detected, making its runtime depend on how many leading bytes match. Over multiple observations, attackers can measure these timing variations to gradually deduce authentication secrets.

Why is This a Concern for Authentication Systems?

Authentication processes rely on comparing secrets like client proofs and server signatures. If an attacker can trigger or observe multiple authentication attempts, even micro-second differences in response times can leak valuable information.

While such attacks require precise timing measurements and stable network conditions, any non-constant-time comparison is inherently unsafe in cryptographic contexts. Hence, even low-risk timing differences are considered critical security flaws in authentication flows.

How Was CVE-2025-59432 Fixed?

The fix was implemented in this commit.

Technical Fix Overview:

• Previous behavior:
  • Used Arrays.equals(byte[], byte[]) for secret comparisons - non-constant time.
• Updated behavior:
  • Replaced with MessageDigest.isEqual(byte[], byte[]), which performs constant-time comparison and prevents timing-based information leakage.
• Additional improvements:
  • Updated forbidden API checks to flag and prevent future use of insecure comparison methods.

By ensuring all comparisons are done in constant time, this update eliminates the timing side-channel vulnerability.

What Are the Best Practices to Prevent Timing Attacks?

Developers and security engineers should follow these recommendations:

1. Always use constant-time comparison functions (like MessageDigest.isEqual in Java).
2. Avoid leaking information through error messages or inconsistent response behaviors.
3. Review cryptographic code for data-dependent timing variations.
4. Conduct periodic security audits of third-party authentication libraries.

Organizations should ensure they’re running the patched version to avoid exposure.

At Loginsoft, our Vulnerability Intelligence (LOVI) team continuously monitors emerging CVEs like CVE-2025-59432 to help developers and security engineers stay ahead of risks.

Stay informed with Vulnerability Intelligence for real-time updates, technical deep dives, and remediation insights.

References/Resources:

https://github.com/advisories/GHSA-3wfh-36rx-9537

https://nvd.nist.gov/vuln/detail/CVE-2025-59432

https://github.com/ongres/scram?tab=readme-ov-file#overview

https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/security/MessageDigest.html#isEqual(byte%5B%5D,byte%5B%5D

https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2025-59432

FAQ: People Also Ask

1. What is CVE-2025-59432?

It’s a timing attack vulnerability in the com.ongres.scram:scram-common Java library that could allow attackers to infer authentication secrets.

2. How does a timing attack work in SCRAM authentication?

By measuring tiny differences in response time during secret comparison, attackers can deduce how many bytes match - revealing partial secret information over time.

3. How was CVE-2025-59432 fixed?

Developers replaced Arrays.equals() with MessageDigest.isEqual(), which performs constant-time comparisons, removing time-based leakage.

4. What should developers do to stay protected?

Update to the latest patched version, review your code for non-constant-time operations, and follow secure coding best practices for cryptography.

5. Why are constant-time comparisons important in authentication?

They ensure that response time doesn’t vary with data content, preventing attackers from exploiting timing differences to guess secret information.