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Fencer Intel
medium 5.9

CVE-2026-3416 json

Predictable Pseudorandom Number Generation via Webhook HMAC Secret Generation in Multiple WSO2 Products Allows Forged Event Payloads

published 2mo ago modified last mo. also EUVD-2026-70453

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits
0
none known

Summary

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.

Patch / fix

  • WSO2 WSO2 API Manager 4.1.0.253, 4.2.0.193, 4.3.0.104, 4.4.0.68, 4.5.0.52
  • WSO2 WSO2 API Control Plane 4.5.0.53

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2mo ago

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

  • WSO2 WSO2 API Manager
  • WSO2 WSO2 API Control Plane

Classification

Weakness
  • CWE-330 Use of Insufficiently Random Values

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.