CVE-2018-11784: When the default servlet in Apache Tomcat versions 9.0.0.M1 to 9.0.11, 8.5.0 to 8.5.33 and 7.0.23 to 7.0.90 re

This week

MEDIUM 4.3WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2018-11784 is a medium-severity flaw (CVSS 4.3) affecting tomcat, debian linux, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

When the default servlet in Apache Tomcat versions 9.0.0.M1 to 9.0.11, 8.5.0 to 8.5.33 and 7.0.23 to 7.0.90 returned a redirect to a directory (e.g. redirecting to '/foo/' when the user requested '/foo') a specially crafted URL could be used to cause the redirect to be generated to any URI of the attackers choice.

Why this priority

EPSS top 1%: very likely to be exploited
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	97.7% (top 1%)
CISA exploited list	No
Weakness	CWE-601
Published	2018-10-04
Last modified	2026-10-15

Publisher (CNA): Apache Software Foundation · Vendor: apache · canonical · debian · netapp · redhat

Last updated 2026-10-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-10-04 13:29 UTCPublished CVE record published
2026-10-15 18:17 UTCUpdated Record last modified

apache tomcat UPGRADE

Affected: >= 7.0.23 and <= 7.0.90 · >= 8.5.0 and <= 8.5.33 · >= 9.0.1 and <= 9.0.11 · 9.0.0 · 9.0.0 milestone1 · 9.0.0 milestone10 · 9.0.0 milestone11 · 9.0.0 milestone12

Fixed in: newer than 9.0.11

Safe to downgrade to: a release before 7.0.23

1. Check installed version

apt-cache policy tomcat || rpm -q tomcat || tomcat --version

2. UPGRADE to newer than 9.0.11 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade tomcat

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tomcat

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 7.0.23 (Debian / Ubuntu)

apt-cache madison tomcat sudo apt install tomcat=<VERSION_BEFORE_7.0.23> sudo apt-mark hold tomcat

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list tomcat sudo dnf downgrade tomcat-<VERSION_BEFORE_7.0.23> sudo dnf versionlock add tomcat

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

debian debian linux MITIGATE

Affected: 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

canonical ubuntu linux MITIGATE

Affected: 14.04 · 16.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 14.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

netapp snap creator framework MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy snap-creator-framework || rpm -q snap-creator-framework || snap-creator-framework --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

redhat enterprise linux desktop MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux server MITIGATE

Affected: 7.0 · 7.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: Apache Tomcat 9.0.0.M1 - Open Redirect
Nuclei scan template: Apache Tomcat - Open Redirect

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2018-11784?

tomcat: upgrade to newer than 9.0.11; debian linux: mitigate or apply the listed mitigation; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-11784 being exploited?

CVE-2018-11784 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2018-11784 affect?

CVE-2018-11784 affects tomcat, debian linux, ubuntu linux. Severity is medium (CVSS 4.3). When the default servlet in Apache Tomcat versions 9.0.0.M1 to 9.0.11, 8.5.0 to 8.5.33 and 7.0.23 to 7.0.90 returned a redirect to a directory (e.g. redirecting to '/foo/' when the user requested '/foo') a specially crafted URL could be use

How urgent is CVE-2018-11784?

Priority 50/100. EPSS top 1%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

Apache Tomcat vulnerabilities · Ubuntu vulnerabilities · Debian vulnerabilities

Related CVEs

CVE-2026-34486 HIGH 7.5 EXPLOITED DOWNGRADE DOWNGRADE Apache Tomcat Missing Encryption of Sensitive Data Vulnerability
CVE-2026-29146 HIGH 7.5 UPGRADE Padding Oracle vulnerability in Apache Tomcat's EncryptInterceptor with default configuration. This issue aff
CVE-2026-25854 MEDIUM 6.1 UPGRADE Occasional URL redirection to untrusted Site ('Open Redirect') vulnerability in Apache Tomcat via the LoadBala
CVE-2026-29145 CRITICAL 9.1 UPGRADE UPGRADE CLIENT_CERT authentication does not fail as expected for some scenarios when soft fail is disabled vulnerabili
CVE-2026-24880 HIGH 7.5 UPGRADE Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Tomca

References

← Back to latest CVEs