Apache Nutch: Use of Externally-Controlled Input to Select Classes or Code
CVE-2026-41871 is a critical-severity use of externally-controlled input to select classes or code vulnerability in Apache Nutch 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. Affected Apache Nutch versions: 1.10 through 1.22. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.74% chance of exploitation within 30 days, higher than 55% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Nutch to 1.23 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 Nutch | 1.10 through 1.22 | Not stated |
| Apache | Nutch | 1.10 up to, but not including, 1.23 | 1.23 |
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 CISA (ADP).
Official description
Missing Authorization, Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') vulnerability in Apache Nutch Server (Nutch REST API). This issue affects Apache Nutch: from 1.10 through 1.22. Users are recommended to upgrade to version 1.23, which removes the Nutch Server. If an upgrade is not possible, user must restrict access to instances running the Nutch Service to trusted users only. Please, also visit the Apache Nutch security advisories https://nutch.apache.org/documentation/security/ .
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use of Externally-Controlled Input to Select Classes or Code
The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code.
How developers prevent this class of flaw
- Refactor your code to avoid using reflection.
- Do not use user-controlled inputs to select and load classes or code.
- Apply strict input validation by using allowlists or indirect selection to ensure that the user is only selecting allowable classes or code.
More Use of Externally-Controlled Input to Select Classes or Code vulnerabilities (CWE-470)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- openwall.com/lists/oss-security/2026/09/08/5Mailing List, Third Party Advisory
Other vulnerabilities in Apache Nutch
- 8.8 High severity
- 9.1 Critical severity
Recent Use of Externally-Controlled Input to Select Classes or Code vulnerabilities
- 9.1 Critical severity
PaperCut NG/MF Unsafe Reflection Exploited
- 8.8 High severity
- 7.5 High severity
- 7.2 High severity
- 9.8 Critical severity
- 7.2 High severity
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