Detection Guidance

This vulnerability involves the netty incubator codec.bhttp library versions prior to 0.0.21.Final producing all-zero byte arrays as key material silently on failure, which is difficult to detect directly on a network or system.

Since the issue is internal to the HPKEContext implementation and manifests as silent failures returning zero-filled byte arrays, detection would primarily involve verifying the version of the netty-incubator-codec-ohttp library in use.

You can check the version of the netty-incubator-codec-ohttp dependency in your Java project by inspecting your build files or using commands like:

• For Maven projects: mvn dependency:list | grep netty-incubator-codec-ohttp
• For Gradle projects: ./gradlew dependencies --configuration runtimeClasspath | grep netty-incubator-codec-ohttp

If the version is older than 0.0.21.Final, your system is vulnerable.

Additionally, monitoring application logs for exceptions related to HPKEContext operations (such as CryptoException after patching) or unexpected cryptographic failures might help detect attempts to exploit this issue, but prior to patching, failures are silent and produce no error.

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Executive Summary

The vulnerability in netty incubator codec.bhttp involves the HPKE (Hybrid Public Key Encryption) implementation where certain functions like HKDF_expand and EVP_HPKE_CTX_export return non-NULL but invalid outputs on failure. Specifically, they return byte arrays filled with zeros that cannot be distinguished from valid outputs.

These zero-filled byte arrays are used as key material for AEAD encryption in the response process. Because the failure is silent and produces a deterministic, attacker-predictable AEAD key, it compromises the security of the encryption.

The issue was fixed in version 0.0.21.Final by modifying the HPKEContext methods to throw exceptions on failure instead of returning invalid data, ensuring that errors are properly handled and invalid keys are not used.

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Impact Analysis

This vulnerability can lead to the use of an all-zero, deterministic AEAD encryption key when certain cryptographic operations fail silently. As a result, encrypted responses could be encrypted with predictable keys, allowing attackers to potentially decrypt or tamper with the data.

Such predictable encryption keys undermine the confidentiality and integrity of communications, exposing sensitive information and enabling attacks such as message forgery or replay.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade the netty-incubator-codec-ohttp library to version 0.0.21.Final or later.

This version patches the issue by modifying the HPKEContext implementations to properly signal failures via exceptions instead of returning empty byte arrays filled with zeros, preventing the use of attacker-predictable AEAD keys.

Ensure that your code handles CryptoException properly when calling HPKEContext methods such as export, extract, and expand, to avoid silent failures.

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Compliance Impact

The vulnerability causes the generation of deterministic, attacker-predictable AEAD keys due to silent failures producing all-zero key material. This undermines the confidentiality and integrity of encrypted data, which are critical requirements under common standards and regulations such as GDPR and HIPAA.

By potentially allowing attackers to predict encryption keys, this flaw could lead to unauthorized data access or data breaches, thereby violating data protection obligations mandated by these regulations.

Therefore, systems using vulnerable versions of the netty-incubator-codec-ohttp library may fail to meet the security controls required for compliance until they apply the patch in version 0.0.21.Final.

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