How severe is CVE-2017-12165?

CVE-2017-12165 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2017-12165?

CVE-2017-12165 affects the following packages: io.undertow:undertow-core (Maven), io.undertow:undertow-core (Maven), io.undertow:undertow-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2017-12165?

Update io.undertow:undertow-core to 1.3.31 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-12165 is resolved across your whole dependency graph.

How do I detect CVE-2017-12165 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2017-12165 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2017-12165 actively exploited in the wild?

No public exploit code has been indexed for CVE-2017-12165 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2017-12165?

CVE-2017-12165 has an EPSS (Exploit Prediction Scoring System) score of 1.9%, placing it in the 79th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2017-12165?

CVE-2017-12165 is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2017-12165 published, and has it been updated?

CVE-2017-12165 was published on July 27, 2018 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2017-12165 — undertow-core

HIGHFix: undertow-io/undertow@1e72647

CVE-2017-12165 is a high-severity (CVSS 7.5) CWE-444 vulnerability in io.undertow:undertow-core. A fix is available for io.undertow:undertow-core — see the affected versions and patch details below.

Undertow Request Smuggling vulnerability

Also known asGHSA-5gg7-5wv8-4gcj

Published

Jul 27, 2018

Updated

Oct 24, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Nov 3, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.9%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected

☕io.undertow:undertow-core☕io.undertow:undertow-core☕io.undertow:undertow-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

It was discovered that Undertow before 1.4.17, 1.3.31 and 2.0.0 processes http request headers with unusual whitespaces which can cause possible http request smuggling.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.undertow:undertow-core`	all versions	1.3.31`io.undertow:undertow-core:1.3.31`
☕Maven	`io.undertow:undertow-core`	≥ 1.4.0&&< 1.4.17	1.4.17`io.undertow:undertow-core:1.4.17`
☕Maven	`io.undertow:undertow-core`	≥ 2.0.0.Alpha1&&< 2.0.0.Beta1	2.0.0.Beta1`io.undertow:undertow-core:2.0.0.Beta1`

Affected Products

2 products · 5 configurations

Application

jboss enterprise application platformredhat

2 versions

7.0.07.1.0

Application

undertowredhat

≥ 1.4.0 && < 1.4.17

1 version

2.0.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.undertow:undertow-core to 1.3.31 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-12165 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatLow

Product	Fixed in	Advisory
Red Hat JBoss A-MQ 6.3	see advisory	RHSA-2018:1322
Red Hat JBoss EAP 7	see advisory	RHSA-2017:3456
Red Hat JBoss EAP 7	`undertow`	RHSA-2018:0003
Red Hat JBoss Enterprise Application Platform 7.0 for RHEL 6	`eap7-activemq-artemis-0:1.1.0-19.SP24_redhat_1.1.ep7.el6`	RHSA-2018:0002
Red Hat JBoss Enterprise Application Platform 7.0 for RHEL 6	`eap7-jboss-ec2-eap-0:7.0.9-2.GA_redhat_2.ep7.el6`	RHSA-2018:0005
Red Hat JBoss Enterprise Application Platform 7.0 for RHEL 7	`eap7-activemq-artemis-0:1.1.0-19.SP24_redhat_1.1.ep7.el7`	RHSA-2018:0004
Red Hat JBoss Enterprise Application Platform 7.1 for RHEL 6	`eap7-activemq-artemis-0:1.5.5.008-1.redhat_1.1.ep7.el6`	RHSA-2017:3454
Red Hat JBoss Enterprise Application Platform 7.1 for RHEL 6	`eap7-jboss-ec2-eap-0:7.1.0-5.GA_redhat_5.ep7.el6`	RHSA-2017:3458

Frequently Asked Questions

It was discovered that Undertow before 1.4.17, 1.3.31 and 2.0.0 processes http request headers with unusual whitespaces which can cause possible http request smuggling.

O3 Security · Impact-Aware SCA

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