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CVE-2026-82617: Product identification pending

Severity

10 (CRITICAL)

Vendor

APACHE

Affected versions

Apache OpenNLP: 2.0.0 through 2.5.11; 3.0.0-M1 through 3.0.0-M5

Fixed version

2.5.12, or 3.0.0-M6

Patch status

Patched

Published

2026-09-11T18:16:59.443

Modified

2026-09-11T21:17:25.553

Why it matters

This vulnerability allows an unauthenticated attacker to cause a Denial of Service (DoS) by supplying specially crafted text for analysis. This can lead to excessive CPU consumption, potentially minutes of pinned CPU, or cause application threads to terminate unexpectedly, severely impacting service

Recommended admin actions

• Identify all systems using Apache OpenNLP within your environment.
• Upgrade Apache OpenNLP to version 2.5.12 (for 2.x users) or 3.0.0-M6 (for 3.0.0 milestone users).
• Review application configurations to ensure untrusted input is properly sanitized before analysis by name-finder patterns.
• Monitor CPU usage and thread status for applications utilizing OpenNLP for any anomalies.

Technical summary

The two built-in name-finder patterns exposed by opennlp.tools.namefind.RegexNameFinderFactory – DEFAULT_REGEX_NAME_FINDER.EMAIL and DEFAULT_REGEX_NAME_FINDER.URL – contain ambiguous nested quantifiers. An application that obtains these finders through RegexNameFinderFactory.getDefaultRegexNameFinders(…) and then applies them to untrusted text through RegexNameFinder.find(String[]) or RegexNameFinder.find(String) can be driven into super-linear backtracking or into unbounded matcher recursion by a small crafted input. For the EMAIL pattern, a long run of local-part characters that is never followed by an @ forces the matcher to re-scan to end-of-input from every starting offset. Cost grows quadratically with input length: an input of approximately 32 KB consumes several seconds of CPU in a single find() call and returns no match, and each doubling of the input multiplies the cost roughly four-fold. For the URL pattern, the query-string sub-expression nests a capturing repetition inside an outer repetition. The JDK matcher recurses once per query token, so an input of approximately 4 KB containing many &-separated tokens exhausts the thread stack and causes java.lang.StackOverflowError to propagate out of find(), terminating the calling thread. On a thread created with a smaller stack (for example -Xss512k, typical of server worker pools) approximately 1 KB is sufficient. In both cases an attacker who can supply text for analysis can convert a single request into seconds to minutes of pinned CPU, or into an abrupt thread death, denying service to the embedding application. No authentication, special configuration, or model file is required beyond the application having selected one of the two built-in finders. This issue affects Apache OpenNLP: from 2.0.0 through 2.5.11; from 3.0.0-M1 through 3.0.0-M5. Users are recommended to upgrade to version 2.5.12, or to 3.0.0-M6 for users tracking the 3.0.0 milestone line, which fix the issue.

View the official NVD record for CVE-2026-82617

AI-enriched (HIGH confidence). Validate against the vendor advisory before taking production action.