CVE-2026-82617

The two built-in name-finder patterns exposed by

opennlp.tools.namefind.RegexNameFinderFactory - DEFAULTREGEXNAME_FINDER.EMAIL

and DEFAULTREGEXNAME_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.

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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.

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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.

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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.

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This issue affects Apache OpenNLP: from 2.0.0 through 2.5.11; from 3.0.0-M1 through

3.0.0-M5.

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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.