CVE-2026-87779 in Syncope
Summary
by MITRE • 09/14/2026
Insertion of sensitive information into log file vulnerability in Apache Syncope.
When AES key of non-standard length (not 16/24/32 bytes) is configured, Syncope will pad the provided value with random characters. The resulting key value is logged.
This issue affects Apache Syncope: from 3.0.15 through 3.0.16, from 4.0.3 through 4.0.7, from 4.1.0-M0 through 4.1.2.
Users are recommended to upgrade to version 4.0.8 / 4.1.3, which fix this issue.
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Analysis
by VulDB Data Team • 09/14/2026
The vulnerability identified in Apache Syncope represents a critical information disclosure flaw rooted in improper handling of cryptographic key material during the logging process. This specific weakness allows sensitive security credentials to be written into log files where they may be accessible to unauthorized individuals or automated monitoring systems that do not have strict access controls for secret data. The core technical issue arises when an administrator configures an Advanced Encryption Standard AES key with a length that deviates from the standard requirements of 16, 24, or 32 bytes. In such cases, Apache Syncope attempts to accommodate the non-standard input by padding the provided value with random characters to meet internal processing expectations. However, rather than masking this sensitive material in the application logs, the system records the resulting padded key string directly into the log output. This behavior exposes the original secret component along with the generated padding, effectively compromising the confidentiality of the encryption key used for securing data within the Syncope environment.
From a technical perspective, this flaw is classified under CWE-532, which covers the insertion of sensitive information into log files. The vulnerability stems from a failure to implement proper sanitization or redaction mechanisms before writing cryptographic material to persistent storage such as application logs. In many enterprise environments, log files are aggregated by centralized logging solutions like ELK Stack, Splunk, or Graylog for analysis and monitoring purposes. These systems often retain data for extended periods and may be accessible to a broader range of personnel than the primary application servers themselves. Consequently, an attacker with read access to these logs can extract the AES key, potentially decrypting sensitive user data protected by Syncope if they also have access to the encrypted payloads or session tokens associated with that key. This scenario is particularly dangerous in cloud-native deployments where log streams are frequently transmitted over networks and stored in object storage services like AWS S3 or Azure Blob Storage, which might not be configured with strict encryption at rest policies for all data types.
The operational impact of this vulnerability extends beyond the immediate exposure of a single key. If an attacker obtains the AES key used by Apache Syncope, they may gain the ability to decrypt sensitive identity management data stored within the system or intercept and manipulate communication channels secured by that key depending on its specific usage scope. This compromises the integrity and confidentiality guarantees provided by the security architecture. Furthermore, because the padding involves random characters, each instance of logging might produce a different string representation even for the same underlying secret if not handled consistently, but in this case, the deterministic nature of the bug means the padded version is logged predictably enough to be useful once extracted. The affected versions span from 3.0.15 through 3.0.16 and from 4.0.3 through 4.0.7 as well as early milestones in the 4.1 series up to 4.1.2, indicating that this issue persisted across multiple minor releases before being addressed.
Mitigation strategies primarily involve upgrading Apache Syncope to version 4.0.8 or 4.1.3 and later, where the developers have implemented fixes to prevent sensitive key material from being written to logs in plaintext. In addition to applying these software updates, organizations should conduct a thorough review of existing log files generated by affected versions to identify any instances where AES keys may have been exposed. If such exposure is confirmed, it is imperative to rotate all cryptographic keys immediately and invalidate any sessions or tokens that were protected using the compromised key. To prevent future occurrences, security teams should enforce strict logging policies that prohibit the inclusion of secrets in log outputs by default. This can be achieved through static code analysis tools configured to detect CWE-532 patterns during development and by implementing runtime application self-protection mechanisms that sanitize sensitive data before it reaches any output stream. Regular audits of configuration files and deployment scripts should also verify that non-standard key lengths are avoided or properly handled without exposing the underlying secrets in diagnostic outputs.