CVE-2026-40682: Apache Opennlp XML external entity (XXE) (CVSS 9.1)

Description

XML External Entity (XXE) via Unsanitized Dictionary Parsing in Apache OpenNLP DictionaryEntryPersistor Versions Affected: before 2.5.9, before 3.0.0-M3 Description: The DictionaryEntryPersistor class initializes a static SAXParserFactory at class-load time without enabling FEATURE_SECURE_PROCESSING or disabling DTD processing. When create(InputStream, EntryInserter) is invoked, the only feature set on the XMLReader is namespace support — external entity resolution and DOCTYPE declarations remain fully enabled. An attacker who can supply a crafted dictionary file (e.g., a stop-word list or domain dictionary) containing a malicious DOCTYPE declaration can trigger local file disclosure via file:// entity references or server-side request forgery via http:// entity references during SAX parsing, before the application processes a single dictionary entry. This is inconsistent with the project's own XmlUtil.createSaxParser() helper, which correctly sets FEATURE_SECURE_PROCESSING and disallow-doctype-decl and is used by all other XML parsing paths in the codebase. The public Dictionary(InputStream) constructor delegates directly to this method and is the documented API for loading user-supplied dictionaries, making untrusted input a realistic scenario. Mitigation: 2.x users should upgrade to 2.5.9. 3.x users should upgrade to 3.0.0-M3. Users who cannot upgrade immediately should ensure that all dictionary files are sourced from trusted origins and should consider wrapping the Dictionary(InputStream) constructor with input validation that rejects any XML containing a DOCTYPE declaration before it reaches the parser.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Apache Opennlp< 2.5.9 · 3.0.0

Remediation

Fixed in

Apache Opennlp≥ 2.5.9

Patch & vendor advisories

https://lists.apache.org/thread/r6jpt0qr9nj67gqhppqg7jxf8vsbo0w6

References

https://access.redhat.com/security/cve/CVE-2026-40682
https://bugzilla.redhat.com/show_bug.cgi?id=2466484
https://lists.apache.org/thread/r6jpt0qr9nj67gqhppqg7jxf8vsbo0w6Mailing ListVendor Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40682.json
http://www.openwall.com/lists/oss-security/2026/05/01/19Mailing ListThird Party Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-40682 being actively exploited?

CVE-2026-40682 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.84%.

How severe is CVE-2026-40682?

CVE-2026-40682 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.84% probability of exploitation.

Which products are affected by CVE-2026-40682?

Affected products include Apache Opennlp.

How do I fix CVE-2026-40682?

Upgrade affected software to a fixed version, for example Apache Opennlp 2.5.9 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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