CVE-2026-107177 in Express Gateway
Summary
by MITRE • 10/07/2026
Express Gateway through 1.16.11 contains a hardcoded cryptographic key vulnerability that allows attackers with datastore access to decrypt stored OAuth 2.0 token secrets via the default crypto.cipherKey 'sensitiveKey'. Attackers who can read Redis can decrypt tokenEncrypted values and combine them with stored token IDs to obtain valid bearer tokens for any user.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified in Express Gateway versions through 1.16.11 represents a critical failure in cryptographic key management, specifically categorized under CWE-798: Use of Hard-coded Credentials. This flaw stems from the application's reliance on a static, hardcoded encryption key known as sensitiveKey within its default crypto.cipher configuration. In secure software architecture, secret keys used for encrypting sensitive data such as OAuth 2.0 token secrets must be dynamic, unique to each deployment environment, and stored in protected vaults or environment variables rather than being embedded directly into the source code or default configuration files. By hardcoding this key, Express Gateway ensures that any instance of the software deployed with default settings shares the same decryption capability, effectively nullifying the confidentiality guarantees provided by encryption when the key is exposed.
The operational impact of this vulnerability is severe due to its interaction with the underlying data storage mechanism. Express Gateway utilizes Redis as a datastore for managing session and token information. When OAuth 2.0 tokens are issued, their secrets are encrypted using the aforementioned hardcoded cipherKey before being stored in Redis. An attacker who gains read access to the Redis instance can retrieve these encrypted values, referred to as tokenEncrypted. Because the decryption key is publicly known or easily discoverable through standard configuration inspection, the attacker can trivially decrypt these blobs to reveal the plaintext secret portions of the OAuth tokens. This process does not require complex cryptanalysis; it relies solely on access to the storage medium and knowledge of the default algorithm parameters.
Once the encrypted token secrets are decrypted, they can be combined with stored token IDs to reconstruct valid bearer tokens for any user account managed by the gateway. In the context of OAuth 2.0, possessing both the token ID and its corresponding secret allows an attacker to authenticate as that specific user without needing their password or multi-factor authentication credentials. This capability effectively bypasses all access control mechanisms enforced by the API gateway, granting the attacker full administrative privileges associated with the compromised account. The attack vector aligns closely with MITRE ATT&CK technique T1552.004: Unsecured Credentials, specifically focusing on stored unencrypted or weakly protected credentials within a data store that lacks proper key isolation.
The severity of this issue is compounded by the common deployment practices where developers may overlook changing default configurations during production setup. If an organization deploys Express Gateway without overriding the sensitiveKey with a unique, high-entropy secret generated for their specific environment, they remain vulnerable to any external party who can reach the Redis port or compromise a server with access to it. This is particularly dangerous in cloud environments where misconfigured security groups might inadvertently expose internal data stores like Redis to broader network segments. The ability to decrypt tokens means that even if initial authentication was secure, the persistence of those credentials becomes compromised once the storage layer is accessed by an unauthorized entity.
Mitigation strategies must focus on immediate remediation and long-term cryptographic hygiene. First and foremost, organizations running Express Gateway versions up to 1.16.11 should upgrade to a patched version where this vulnerability has been addressed or implement strict configuration overrides if upgrading is not immediately feasible. It is imperative to replace the default sensitiveKey with a strong, randomly generated secret that is unique to each deployment instance. This new key must be stored securely, preferably using environment variables managed by infrastructure-as-code tools or dedicated secrets management services like HashiCorp Vault or AWS Secrets Manager, rather than in plaintext configuration files committed to version control systems.
Furthermore, access controls for the Redis datastore must be rigorously audited and hardened. The Redis instance should not be exposed on public-facing interfaces and must require authentication if network-level isolation is insufficient. Network segmentation policies should ensure that only authorized application servers can communicate with the Redis backend. Additionally, implementing regular rotation of encryption keys where supported by the gateway version adds a layer of defense-in-depth, ensuring that even if an old key were to be compromised in the future, its utility would be limited to data encrypted before the rotation event. Continuous monitoring for unusual access patterns to the datastore can also help detect potential exploitation attempts early.