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TomcatWeb server / proxy · Apache

CVE-2021-42340

HIGH · 7.5 CVSS v3.1 Published 2021-10-14
Fix available
A fix is available. Upgrade to 8.5.72 / 9.0.54 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
TomcatWeb server / proxy
Affected:>= 8.5.60, < 8.5.72>= 9.0.40, < 9.0.54>= 10.0.1, < 10.0.12= 10.0.0= 10.1.0
Debian LinuxOperating system
Affected:= 11.0
HciApplication
Affected:all versions
Management Services For Element SoftwareApplication
Affected:all versions
Agile Engineering Data ManagementApplication
Affected:= 6.2.1.0
Big Data Spatial And GraphApplication
Affected:< 23.1
Communications Diameter Signaling RouterApplication
Affected:>= 8.0.0.0, <= 8.5.0.2
Hospitality Cruise Shipboard Property Management SystemApplication
Affected:= 20.1.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 8.5.72 / 9.0.54 / 10.0.12 or later
Fixed in 8.5.729.0.5410.0.12
Vendor patch www.oracle.com →
Recommended fix High confidence

Tomcat 8.5.72+, 9.0.54+, or 10.0.12+ (or migrate to 10.1.x/11.x stable releases)

  1. 1. Identify the current Apache Tomcat version by checking the $CATALINA_HOME/README RELEASE-NOTES or running: catalina.sh version
  2. 2. For Tomcat 8.5.x: Upgrade to version 8.5.72 or later (e.g., 8.5.73, 8.5.74, etc.)
  3. 3. For Tomcat 9.0.x: Upgrade to version 9.0.54 or later (e.g., 9.0.55, 9.0.56, etc.)
  4. 4. For Tomcat 10.0.x: Upgrade to version 10.0.12 or later (10.0.13, 10.0.14, etc.) or migrate to 10.1.x/11.x
  5. 5. Download from official Apache Tomcat repository: https://tomcat.apache.org/download-80.cgi, https://tomcat.apache.org/download-90.cgi, or https://tomcat.apache.org/download-100.cgi
  6. 6. Stop the Tomcat service: systemctl stop tomcat or catalina.sh stop
  7. 7. Backup the existing Tomcat installation directory
  8. 8. Extract the new version and copy configuration files (server.xml, context.xml, etc.) from the backup
Caveat Major version upgrades (e.g., 10.0.x to 10.1.x) may require code changes for WebSocket and JSP API differences; review migration guide before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-42340 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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