Apache Lucene.Net: Improper Restriction of XML External Entity Reference
CVE-2026-47898 is a critical-severity improper restriction of XML external entity reference vulnerability in Apache Lucene.Net from Apache, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 4.8.0-beta00018 as the first without the flaw, so updating Apache Lucene.Net to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.47% 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 Apache Lucene.Net to 4.8.0-beta00018 or a later version.
- Read the advisory on lists.apache.org 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 |
|---|---|---|---|
| Apache | Apache Lucene.Net | 4.8.0-beta00005 up to, but not including, 4.8.0-beta00018 | 4.8.0-beta00018 |
| Apache | Lucene.net | 4.8.0 | 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
- 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:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 4.0 | Medium | CNA (apache.org) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
Improper Restriction of XML External Entity Reference vulnerability in Apache Lucene.Net (Lucene.Net.Analysis.Common library). This issue affects Apache Lucene.Net.Analysis.Common: from 4.8.0-beta00005 before 4.8.0-beta00018. Users are recommended to upgrade to version 4.8.0-beta00018, which fixes the issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of XML External Entity Reference
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.
How developers prevent this class of flaw
- Many XML parsers and validators can be configured to disable external entity expansion.
More Improper Restriction of XML External Entity Reference vulnerabilities (CWE-611)
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
Third-party and government advisories
- openwall.com/lists/oss-security/2026/07/03/3Mailing List, Third Party Advisory
Other vulnerabilities in Apache Lucene.Net
- 7.5 High severity
- 7.5 High severity
Recent Improper Restriction of XML External Entity Reference vulnerabilities
- 9.1 Critical severity
- 8.5 High severity
- 9.8 Critical severity
- 8.2 High severity
- 7.4 High severity
- 7.7 High severity
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