CVE-2025-68702: Jervis Library Hash Padding Vulnerability

CVE-2025-68702 Overview

CVE-2025-68702 is a cryptographic vulnerability in Jervis, a library used for Job DSL plugin scripts and shared Jenkins pipeline libraries. Prior to version 2.2, Jervis incorrectly implements SHA-256 hash padding by using padLeft(32, '0') instead of the correct padLeft(64, '0'). Since SHA-256 produces 32 bytes, which translates to 64 hexadecimal characters, this implementation error results in truncated hash representations that could undermine integrity verification mechanisms.

Critical Impact

The incorrect hash padding implementation can lead to hash collisions and integrity verification bypasses, potentially allowing attackers to substitute malicious content that produces matching truncated hashes.

Affected Products

• Jervis versions prior to 2.2
• Jenkins environments using vulnerable Jervis library for Job DSL plugin scripts
• Jenkins shared pipeline libraries utilizing Jervis for hash operations

Discovery Timeline

• 2026-01-13 - CVE CVE-2025-68702 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2025-68702

Vulnerability Analysis

This vulnerability falls under CWE-327 (Use of a Broken or Risky Cryptographic Algorithm). The core issue stems from an implementation error in how SHA-256 hash values are formatted for comparison or storage. SHA-256 is a cryptographic hash function that produces a 256-bit (32-byte) digest. When represented in hexadecimal format, each byte requires two characters, resulting in a 64-character string.

The Jervis library incorrectly used padLeft(32, '0') to ensure consistent hash string lengths. This means that any SHA-256 hash with leading zeros would be truncated to only 32 characters instead of the full 64 characters. This truncation effectively reduces the entropy of the hash comparison from 256 bits to approximately 128 bits, significantly weakening the cryptographic strength and potentially enabling collision attacks where different inputs produce matching truncated outputs.

Root Cause

The root cause is a programming error where the developer confused byte length with hexadecimal character length. When working with SHA-256 hashes:

• SHA-256 produces 32 bytes of output
• In hexadecimal representation, this equals 64 characters
• The incorrect padLeft(32, '0') call only accommodates 32 characters
• The correct implementation should use padLeft(64, '0') to preserve the full hash

This type of error is common when developers work with cryptographic functions and fail to account for the byte-to-hex conversion factor of 2x.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker could potentially:

1. Identify hash comparison operations within Jenkins pipelines using Jervis
2. Generate content that produces a SHA-256 hash with sufficient leading zeros to cause truncation
3. Craft malicious payloads that match the truncated hash of legitimate content
4. Bypass integrity checks that rely on these weakened hash comparisons

The attack complexity is low since the vulnerability is inherent in the library's hash handling code and affects all hash operations performed by vulnerable Jervis versions. The GitHub Security Advisory provides additional technical context on the vulnerability scope.

Detection Methods for CVE-2025-68702

Indicators of Compromise

• Presence of Jervis library versions prior to 2.2 in Jenkins installations
• Jenkins pipeline logs showing hash comparison operations with 32-character hash strings instead of 64 characters
• Unexpected hash validation successes for modified or potentially malicious content
• Job DSL scripts or shared libraries importing vulnerable Jervis versions

Detection Strategies

• Audit Jenkins plugin dependencies for Jervis library version using jenkins-cli.jar list-plugins or similar tools
• Search for padLeft(32, '0') patterns in custom pipeline library code that may have copied the vulnerable pattern
• Monitor integrity verification logs for hash string length anomalies
• Implement automated dependency scanning in CI/CD pipelines to flag vulnerable library versions

Monitoring Recommendations

• Deploy SentinelOne Singularity XDR to monitor Jenkins infrastructure for anomalous build behaviors
• Enable verbose logging for Jenkins pipeline executions to capture hash operation details
• Implement alerting for any integrity check failures or unexpected content modifications in pipeline artifacts
• Track library dependency updates across Jenkins installations using software composition analysis (SCA) tools

How to Mitigate CVE-2025-68702

Immediate Actions Required

• Upgrade Jervis library to version 2.2 or later immediately
• Audit all Jenkins pipelines and Job DSL scripts for direct use of the vulnerable hash padding pattern
• Review any cached or stored hash values that may have been generated with the truncated format
• Regenerate and re-verify any integrity hashes created using the vulnerable Jervis version

Patch Information

The vulnerability is fixed in Jervis version 2.2. The fix corrects the padLeft call from 32 to 64 characters to properly accommodate the full SHA-256 hexadecimal representation. The commit c3981ff contains the specific code changes addressing this vulnerability.

To update Jervis in your Jenkins environment, update your dependency configuration to require version 2.2 or newer. If using Maven, update the version in your pom.xml. For Gradle-based projects, update the dependency declaration in build.gradle.

Workarounds

• If immediate upgrade is not possible, implement wrapper functions that enforce 64-character hash padding before any comparison operations
• Manually patch the vulnerable code pattern in local Jervis installations by changing padLeft(32, '0') to padLeft(64, '0')
• Implement additional integrity verification mechanisms that do not rely on the vulnerable Jervis hash functions
• Consider temporarily disabling hash-based integrity checks until the library can be updated

# Configuration example
# Update Jervis dependency in Gradle build file
# build.gradle
dependencies {
    implementation 'net.gleske:jervis:2.2'
}

# Or in Maven pom.xml
# <dependency>
#     <groupId>net.gleske</groupId>
#     <artifactId>jervis</artifactId>
#     <version>2.2</version>
# </dependency>