Apache CXF: Improper Restriction of Recursive Entity References in DTDs
CVE-2026-108039 is a high-severity improper restriction of recursive entity references in dtds vulnerability in Apache CXF from Apache, 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. The record lists versions 4.2.4, 4.1.9, 3.6.13 as the first without the flaw, so updating Apache CXF to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.46% 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
- Update Apache CXF to 4.2.4 or 4.1.9 or 3.6.13, whichever matches your release line, or a later version.
- Update Cxf to 3.6.13 or 4.1.9 or 4.2.4, whichever matches your release line, 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 CXF | 4.2.0 up to, but not including, 4.2.4; 4.0.0 up to, but not including, 4.1.9; before 3.6.13 | 4.2.4, 4.1.9, 3.6.13 |
| Apache | Cxf | before 3.6.13; 4.0.0 up to, but not including, 4.1.9; 4.2.0 up to, but not including, 4.2.4 | 3.6.13, 4.1.9, 4.2.4 |
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 CISA (ADP).
Official description
By default, StaxUtils placed no limit on the total number of elements or the total number of characters in an XML document. A very large request could therefore use a lot of memory and CPU during parsing, especially where CXF builds a DOM from the input (for example SAAJ or WS-Security), and could cause a denial of service when no request size limit was configured. Both limits now have defaults: the maximum element count is 100 × maxChildElements (5,000,000 by default), and the maximum document size is 256M characters. Applications that process larger documents can raise the limits with the org.apache.cxf.stax.maxElementCount and org.apache.cxf.stax.maxXMLCharacters properties. Users are recommended to upgrade to versions 4.2.4 or 4.1.9 or 3.6.13, which fix this issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Restriction of Recursive Entity References in DTDs
The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.
How developers prevent this class of flaw
- If possible, prohibit the use of DTDs or use an XML parser that limits the expansion of recursive DTD entities.
- Before parsing XML files with associated DTDs, scan for recursive entity declarations and do not continue parsing potentially explosive content.
More Improper Restriction of Recursive Entity References in DTDs vulnerabilities (CWE-776)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- lists.apache.org/thread.html/ms2gbpof609o0v1bjlzb1rn7fwh61l1jIssue Tracking, Mailing List
Third-party and government advisories
- openwall.com/lists/oss-security/2026/10/09/14Mailing List, Third Party Advisory
Other vulnerabilities in Apache CXF
- 7.5 High severity
- 9.1 Critical severity
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 9.1 Critical severity
Recent Improper Restriction of Recursive Entity References in DTDs vulnerabilities
- 7.5 High severity
- 8.7 High severity
- 8.7 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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