Reactor Core: Loop with Unreachable Exit Condition
CVE-2026-47863 is a high-severity loop with unreachable exit condition vulnerability in Reactor Core from Spring, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Reactor Core versions: 3.8.0 through 3.8.6; 3.7.19 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Reactor Core you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on spring.io for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Spring | Reactor Core | 3.8.0 through 3.8.6; 3.7.19 and earlier | Not stated |
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
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.9 | Medium | CNA (vmware.com) |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
In Reactor Core, applications that use the Flux.bufferTimeout operator with fairBackpressure enabled are vulnerable to a Denial of Service (DoS) condition. Reactor Core 3.8.0 - 3.8.6 Reactor Core 3.7.19 and earlier
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Loop with Unreachable Exit Condition
The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.
More Loop with Unreachable Exit Condition vulnerabilities (CWE-835)
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
Advisories
Recent Loop with Unreachable Exit Condition vulnerabilities
- 8.7 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 8.7 High severity
- 7.5 High severity
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