CVE-2026-3416

Analyzed Analyzed - Analysis Complete

Predictable HMAC Secret in API Publisher

Publication date: 2026-09-03

Last updated on: 2026-09-15

Assigner: WSO2 LLC

Description

The API Publisher component previously used a non-cryptographic pseudorandom number generator (PRNG) to create shared secrets for Webhook HMAC validation. This PRNG lacks sufficient entropy for security-sensitive operations, allowing a sophisticated attacker to predict future secrets. This enables malicious actors to forge event payloads with valid HMAC signatures, bypassing the API Gateway's authenticity verification. Successful exploitation could allow an attacker to predict shared secrets used for Webhook HMAC validation and forge event payloads with valid signatures. This may enable bypassing API Gateway authenticity checks, leading to unauthorized event injection, data manipulation, or downstream system compromise.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-03

Last Modified

2026-09-15

Generated

2026-09-23

AI Q&A

2026-09-03

EPSS Evaluated

2026-09-22

NVD

CVE-2026-3416

EUVD

EUVD-2026-70453

Affected Vendors & Products

Vendor	Product	Version / Range
wso2	api_control_plane	From 4.5.0 (inc) to 4.5.0.53 (exc)
wso2	api_manager	From 4.5.0 (inc) to 4.5.0.52 (exc)
wso2	api_manager	From 4.4.0 (inc) to 4.4.0.68 (exc)
wso2	api_manager	From 4.1.0 (inc) to 4.1.0.253 (exc)
wso2	api_manager	From 4.2.0 (inc) to 4.2.0.193 (exc)
wso2	api_manager	From 4.3.0 (inc) to 4.3.0.104 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-330	The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

Attack-Flow Graph

Executive Summary

This vulnerability involves the API Publisher component using a weak non-cryptographic pseudorandom number generator (PRNG) to create shared secrets for Webhook HMAC validation. The PRNG lacks sufficient entropy, allowing attackers to predict future secrets and forge event payloads with valid HMAC signatures. This bypasses authenticity verification in the API Gateway.

Detection Guidance

This vulnerability involves a weak PRNG in WSO2 API Publisher's Webhook HMAC validation. Detection requires checking for predictable shared secrets or invalid HMAC signatures in API Gateway logs. Review WSO2 API Publisher configuration files for PRNG usage and inspect network traffic for forged event payloads with valid HMAC signatures.

Impact Analysis

An attacker could exploit this to predict shared secrets and forge event payloads with valid signatures. This may lead to unauthorized event injection, data manipulation, or compromise of downstream systems through the API Gateway.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling unauthorized data access or manipulation through forged event payloads. Predictable HMAC secrets may allow attackers to bypass authenticity checks, leading to unauthorized event injection or data tampering in systems handling sensitive personal or health data.

Mitigation Strategies

Update the API Publisher component to use a cryptographically secure PRNG for generating shared secrets. Review and regenerate all existing Webhook HMAC shared secrets to prevent prediction by attackers.

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