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9.9
CVE-2026-82617: Apache OpenNLP email or URL parsing can freeze or crash
CVE-2026-82617 · published 14 days ago
Summary
The built-in email and URL patterns used by Apache OpenNLP's name finder can be tricked with specially crafted text. This can make the program use a lot of CPU and even crash with a stack overflow, disrupting any service that processes user‑supplied text. Update to a fixed version or disable those default patterns when handling untrusted input.
What to do
- Update debian apache-opennlp to version 2.5.12-1.
- Update apache opennlp to version 2.5.12 or later.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| – | apache software foundation | apache opennlp |
< 3.0.0-M6 < 2.5.12 |
| Debian:12 | debian | apache-opennlp | All versions |
| Ubuntu:20.04:LTS | canonical | apache-opennlp | All versions |
| – | apache | opennlp |
>= 2.0.0, < 2.5.12 3.0.0 cpe:2.3:a:apache:opennlp:*:*:*:*:*:*:*:* |
| Debian:14 | debian | apache-opennlp |
< 2.5.12-1 Fix: upgrade to 2.5.12-1
|
Original advisory text
Apache OpenNLP, Apache OpenNLP: ReDoS / stack exhaustion in RegexNameFinderFactory built-in EMAIL and URL patterns
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.
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.
References
- https://lists.apache.org/thread/spzhcxxszqdpppg70m1zz2l3mv29mhl3 Vendor Advisory
- https://ubuntu.com/security/CVE-2026-82617 Third Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2026-82617 Third Party Advisory
- http://www.openwall.com/lists/oss-security/2026/09/11/10 URL
- https://security-tracker.debian.org/tracker/CVE-2026-82617 Vendor Advisory
- https://repo.maven.apache.org/maven2 URL
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82617... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-82617 Vendor Advisory
Severity
9.9
Critical
CVSS 4.0: 10.0 (NVD)
Exploitation
EPSS <1%
Type
CWE-1333Inefficient Regular Expression Complexity (ReDoS)
Timeline
Published11 Sep 2026
Updated25 Sep 2026
First seen11 Sep 2026
Sources
CVE-2026-82617 · NVD
CVE-2026-82617 · MITRE
DEBIAN-CVE-2026-82617 · OSV
UBUNTU-CVE-2026-82617 · OSV
CVE-2026-82617 · OSV
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