CVE-2026-102508
CriticalCVSS 9.2Summary
The OPC UA driver in Apache PLC4X (PLC4J) improperly verifies cryptographic signatures and server certificates. An attacker in a network position between client and server can impersonate the OPC UA server and read, forge, or modify secure-channel traffic, including user credentials sent by the client. The issue affects versions 0.9.0 through 0.13.1 and is fixed in version 1.0.0.
Risk Assessment
An organization using affected versions of Apache PLC4X may be subject to a man-in-the-middle attack, resulting in leakage of user credentials and modification of data transmitted over the OPC UA channel. The default security policy of None further increases risk because traffic may be transmitted without encryption.
Recommendation
Upgrade Apache PLC4X to version 1.0.0 as soon as possible, which correctly verifies message signatures, requires server certificate verification against a configured trust store or pinned certificate, and defaults to Basic256Sha256 with SignAndEncrypt. Until the upgrade, avoid connecting to OPC UA servers over untrusted networks.
Other vulnerabilities in Apache PLC4X
See all- CVE-2026-102511High
A vulnerability in the Go implementation of Apache PLC4X (PLC4Go) involves improper verification of the source of a communication channel during ADS discovery. An attacker can send a spoofed UDP datagram to the discovering host, redirecting subsequent connections to an arbitrary address. The connection address is derived from the AmsNetId in the response body rather than the datagram's actual source. Additionally, a single malformed datagram can disable discovery listeners in both PLC4Go and PLC4J implementations, causing panics, exceptions, or infinite loops.
- CVE-2026-102510High
The Go implementation of Apache PLC4X (PLC4Go) contains multiple severe defects, including integer overflow, improper validation of array indices, uncontrolled recursion, and memory allocation with excessive size values. A malicious device or an attacker able to inject network traffic can crash or exhaust the memory of the client application, causing a denial of service.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS