CVE-2026-102509
HIGHDescription
Memory Allocation with Excessive Size Value, Allocation of Resources Without Limits, and Uncontrolled Recursion in the Java implementation of Apache PLC4X (PLC4J) allow a malicious or impersonated device to exhaust the memory or stack of the client application, causing a denial of service. In the OPC UA driver these defects are reachable before authentication: the offending data is parsed while the secure channel and session are being established, before the server's identity has been bound to it. Configuring a trusted server therefore does not prevent exploitation by an attacker who can impersonate it. The individual defects are: - Length-prefixed byte strings are allocated at the size claimed on the wire before the length is checked against the data actually received (0.10.0 through 0.13.1). - Array fields in generated protocol parsers pre-allocate a list with the element count claimed on the wire, allowing a single count field to trigger a multi-gigabyte allocation. This parser is shared by all PLC4J drivers; the OPC UA driver is the verified pre-authentication path (0.10.0 through 0.13.1). - The OPC UA driver accumulates message chunks without enforcing the negotiated maximum chunk count and message size (0.12.0 through 0.13.1). - The OPC UA driver pre-allocates collections using element counts received from the server (0.10.0 through 0.13.1). - Recursive protocol types are parsed without a nesting-depth limit. The same defect in the Go implementation is covered by CVE-2026-102510 https://cveprocess.apache.org/cve5/CVE-2026-102510 . This issue affects Apache PLC4X: from 0.10.0 before 1.0.0. Users are recommended to upgrade to version 1.0.0, which fixes the issue.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v4 Vector
Exploitability
Impact
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploit Intelligence
Low risk: more likely to be exploited than 32% of all known CVEs.
References
Related Vulnerabilities
Other CWE-674 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2021-45105 | Medium | 5.9 | 100% | - | Fix |
| CVE-2024-25111 | High | 8.6 | 65% | - | Fix |
| CVE-2023-50269 | High | 8.6 | 58% | - | Fix |
| CVE-2021-42697 | High | 7.5 | 36% | - | Fix |
| CVE-2007-1285 | High | 7.5 | 19% | - | Fix |
| CVE-2018-0739 | Medium | 6.5 | 19% | - | Fix |
Common questions
How do I fix CVE-2026-102509?
No published fix for CVE-2026-102509 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-102509 being actively exploited?
Not that we know of. CVE-2026-102509 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.40% is the estimated probability that it will be exploited in the next 30 days. That is higher than 32% of all scored CVEs.
How severe is CVE-2026-102509?
CVE-2026-102509 has a CVSS v4 base score of 8.7, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-30.