CVE-2026-34483: Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve component of Apache Tomcat. T

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HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-34483 is a high-severity flaw (CVSS 7.5) affecting tomcat. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve component of Apache Tomcat. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.20, from 10.1.0-M1 through 10.1.53, from 9.0.40 through 9.0.116. Users are recommended to upgrade to version 11.0.21, 10.1.54 or 9.0.117 , which fix the issue.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 60%)
CISA exploited list	No
Weakness	CWE-116
Published	2026-04-09
Last modified	2026-10-26

Publisher (CNA): Apache Software Foundation · Vendor: apache

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-09 20:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

apache tomcat UPGRADE

Affected: >= 9.0.40 and < 9.0.117 · >= 10.1.0 and < 10.1.54 · >= 11.0.0 and < 11.0.21

Fixed in: 9.0.117, 10.1.54, 11.0.21

Safe to downgrade to: a release before 9.0.40

1. Check installed version

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

2. UPGRADE to 9.0.117 (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 9.0.40 (Debian / Ubuntu)

apt-cache madison tomcat sudo apt install tomcat=<VERSION_BEFORE_9.0.40> 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_9.0.40> 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.

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-2026-34483?

tomcat: upgrade to 9.0.117, 10.1.54, 11.0.21. Exact commands for each OS are on this page.

Is CVE-2026-34483 being exploited?

CVE-2026-34483 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-2026-34483 affect?

CVE-2026-34483 affects tomcat. Severity is high (CVSS 7.5). Improper Encoding or Escaping of Output vulnerability in the JsonAccessLogValve component of Apache Tomcat. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.20, from 10.1.0-M1 through 10.1.53, from 9.0.40 through 9.0.116. Use

How urgent is CVE-2026-34483?

Priority 46/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Apache Tomcat vulnerabilities

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References

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