CVE-2026-92899: Apache WSS4J: UsernameToken replay protection bypassed by re-encoding the Nonce

Severity: medium (CVSS 4.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-30 · updated 2026-10-02
Weakness: CWE-290

Description

Apache WSS4J remembers the Nonce of each UsernameToken it accepts, so a captured token cannot be reused. It stored the Nonce as raw base64 text, but authentication decodes that text and uses the bytes.The same bytes can be written as base64 in several ways. An attacker who captured an authenticated request could re-send it with a space added to the Nonce: the password digest still verified, but the token no longer matched the remembered one, so the replay was accepted. Since a UsernameToken does not cover the message body, the captured token could then be reused on requests of the attacker's choosing until it expired. Affects deployments with a nonce replay cache configured, as Apache CXF has by default, and only tokens using a password digest. The cache is now keyed on the decoded Nonce. Users are recommended to upgrade to versions 4.0.2 or 3.0.6 or 2.4.4, which fix this issue.

Affected products

Apache Software Foundation Apache WSS4J: before 2.4.4; from 3.0.0 before 3.0.6; from 4.0.0 before 4.0.2 — fixed in 2.4.4, 3.0.6, 4.0.2

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache WSS4J 2.4.4, 3.0.6, 4.0.2. Check the vendor advisory for mitigations.

References

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