Severity:
CVSS 4.0: 9.2 (critical)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Affected versions:
- Apache PLC4X 0.9.0 before 1.0.0
- Apache PLC4X 1.0.0 unaffected
Description:
Improper Verification of Cryptographic Signature and Improper Certificate
Validation in the OPC UA driver of Apache PLC4X (PLC4J) allows an attacker in a
network position between client and server to impersonate the OPC UA server and
to read, forge or modify secure-channel traffic, including user credential
ssent by the client.
The defect manifests differently depending on the version:
- In 0.9.0 through 0.11.0 a failed message-signature check is only logged and
never enforced, and there is no mechanism to verify the server certificate: it
is taken from the unauthenticated GetEndpoints discovery response and used to
encrypt the user's password.
- In 0.12.0 through 0.13.1 the signature check is inverted (valid signatures
are rejected, invalid ones accepted), and server certificates are accepted
without a trust anchor by default.
- In all affected versions the default security policy is None. Starting with
0.12.0 the driver additionally continues silently at a weaker security policy
than the one configured, and starting with 0.13.0 endpoint selection prefers
the weakest matching endpoint.
Users checking only for one of these mechanisms may wrongly conclude they are
unaffected.
This issue affects Apache PLC4X: from 0.9.0 before 1.0.0.
Users are recommended to upgrade to version 1.0.0, which fixes the issue.
Version 1.0.0 verifies message signatures correctly, refuses to connect unless
the server certificate can be verified against a configured trust store or
pinned certificate, defaults to Basic256Sha256 with SignAndEncrypt, and fails
the
connection if the negotiated security policy is weaker than the configured one.
Credit:
Abhinav Agarwal (finder)
References:
https://plc4x.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-102508
Timeline:
2026-07-09: reported to the Apache Security Team
2026-07-10: fixed on develop (a2dbb6bfc0, 5a4d5bdb4c)
2026-09-07: Apache PLC4X 1.0.0 released with the fix
