OpenJ9: Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
CVE-2026-16441 is a critical-severity reliance on undefined, unspecified, or implementation-defined behavior vulnerability in OpenJ9 from Eclipse Foundation, with a CVSS 3.1 base score of 9.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version 0.60.0 as the first without the flaw, so updating OpenJ9 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.53% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update OpenJ9 to 0.60.0 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Eclipse Foundation | OpenJ9 | 0.8.0 up to, but not including, 0.60.0 | 0.60.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.9 | Medium | CNA (eclipse.org) |
| CVSS 3.1 | 9.6 | Critical | NVD |
Official description
In Eclipse OpenJ9 versions up to 0.60, when executing class files where a previously concrete superclass method has been recompiled as abstract, execution is incorrectly delegated to an interface default method.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Reliance on Undefined, Unspecified, or Implementation-Defined Behavior
The product uses an API function, data structure, or other entity in a way that relies on properties that are not always guaranteed to hold for that entity.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/eclipse-openj9/openj9/pull/24396Issue Tracking
Other vulnerabilities in OpenJ9
- 7.8 High severity
- 7.3 High severity
- 9.1 Critical severity
Recent Reliance on Undefined, Unspecified, or Implementation-Defined Behavior vulnerabilities
- 8.1 High severity
- 9.8 Critical severity
- 7.8 High severity
- 7.1 High severity
- 8.8 High severity
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