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CVE-2026-88920: Apache WSS4J: SAML Sender-Vouches Authentication Bypass

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% 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-287

Description

An authentication bypass in the DOM security processor in Apache WSS4J allows unauthenticated remote attackers to forge authenticated SOAP messages via a crafted unsigned SAML sender-vouches assertion containing an attacker-controlled key. 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

• https://lists.apache.org/thread.html/grt43m3bgbzz0mk0cnho3rcybb1j01z9
• http://www.openwall.com/lists/oss-security/2026/09/30/10

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