CVE-2026-50268: Steeltoe Configuration Encryption OAEP Algorithm Misconfiguration

Technical summary

The vulnerability stems from a misconfiguration in how Steeltoe.Configuration.Encryption constructs the transformation string for BouncyCastle when the `encrypt:rsa:algorithm=OAEP` setting is specified. Instead of enabling OAEP (Optimal Asymmetric Encryption Padding), the incorrect string causes the library to select PKCS#1 v1.5 padding—the same algorithm used by the DEFAULT setting. This represents a cryptographic degradation rather than a complete cipher bypass. An attacker with local system access and administrative privileges could potentially influence encrypted configuration data to exploit weaker-than-expected encryption, though the practical attack surface is narrow. The issue was patched by correcting the BouncyCastle transformation string in version 4.2.0.

Business impact

For organizations using Steeltoe.Configuration.Encryption in cloud-native applications, this bug undermines the security posture of encrypted configuration storage if administrators explicitly chose OAEP expecting stronger protection. If sensitive credentials, API keys, or connection strings are encrypted via configuration and an attacker gains local administrative access, the weaker-than-expected encryption could be compromised more readily than intended. The impact is primarily organizational: breach of encryption policy compliance, potential audit findings regarding cryptographic controls, and exposure of configuration secrets in a compromised environment. Organizations relying on this library for configuration encryption should review their threat model to assess whether the OAEP setting was a requirement.

Affected systems

Steeltoe.Configuration.Encryption versions 4.0.0, 4.0.1, 4.0.2, 4.1.0 and all intermediate releases within that range are affected. Any .NET cloud-native application using these versions of Steeltoe's configuration encryption library with the OAEP algorithm explicitly configured is vulnerable. Applications using the DEFAULT algorithm or versions prior to 4.0.0 are unaffected. Version 4.2.0 and later contain the patch.

Exploitability

Exploitation requires local system access and high-level administrative privileges, making opportunistic or remote exploitation unlikely. An attacker would need to: (1) gain local access to a system running the affected Steeltoe version, (2) possess administrative credentials or equivalent system-level access, and (3) interact with encrypted configuration data. The attack is not remotely exploitable and does not require user interaction. The CVSS score of 1.9 (LOW) reflects these stringent preconditions.

Remediation

Upgrade Steeltoe.Configuration.Encryption to version 4.2.0 or later. This is a straightforward dependency update for .NET projects. Before upgrading, verify that your application actually uses the OAEP configuration setting; if your deployment uses DEFAULT or an older unaffected version, the urgency is lower. After patching, administrators should confirm that the OAEP setting now correctly applies OAEP padding by consulting Steeltoe's release notes or testing against your environment's encryption configuration.

Patch guidance

Update the Steeltoe.Configuration.Encryption NuGet package to version 4.2.0 or later in your project dependencies. Verify the update in your package.lock or packages.config file, rebuild your application, and redeploy. No configuration changes are required post-patch; the corrected transformation string will be applied automatically. Test your encrypted configuration workflow in a staging environment before production deployment to ensure compatibility. Consult the Steeltoe project's release notes on GitHub for any additional breaking changes or migration guidance in version 4.2.0.

Detection guidance

Review your application's Steeltoe.Configuration.Encryption dependency version via package manifests (project.csproj, packages.config, or package.lock files). If versions 4.0.0–4.1.0 are present, identify whether your configuration uses `encrypt:rsa:algorithm=OAEP`. Check application logs and configuration files for explicit OAEP settings. If your deployment uses DEFAULT or does not employ RSA encryption configuration, the vulnerability surface is minimal. Monitor Steeltoe project updates and subscribe to security advisories via the official Steeltoe repository on GitHub.

Why prioritize this

Although the CVSS score is LOW (1.9), this vulnerability should be addressed as part of routine dependency management rather than emergency response. Prioritization depends on your specific use case: if your organization explicitly chose OAEP for enhanced encryption of sensitive configuration data, moving to version 4.2.0 should occur during the next planned maintenance window. If your deployment uses DEFAULT settings or does not store highly sensitive data in encrypted configuration, the risk is minimal. The lack of remote exploitability and requirement for local admin access significantly reduces business urgency.

Risk score, explained

The CVSS 3.1 score of 1.9 reflects the combination of local-only attack vector (AV:L), high complexity (AC:H), high privileges required (PR:H), no user interaction (UI:N), and limited confidentiality impact (C:L) on a single system (S:U). The vulnerability does not enable code execution, denial of service, or integrity modification—only potential exposure of encrypted configuration under a narrow threat scenario. This places it squarely in the LOW severity band and aligns with the practical difficulty of exploitation.

Frequently asked questions