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Low, CVSS 3.7

Apache Tomcat Race Condition vulnerability

CVE-2021-43980GHSA-jx7c-7mj5-9438

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (org.apache.tomcat:tomcat 10.1.0-M14, 10.0.20, 9.0.62, 8.5.78), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Maven org.apache.tomcat:tomcat

    Affected
    >= 8.5.0, < 8.5.78>= 9.0.0-M1, < 9.0.62>= 10.0.0-M1, < 10.0.20>= 10.1.0-M1, < 10.1.0-M14
    Fixed in
    10.1.0-M14, 10.0.20, 8.5.78, 9.0.62

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
3.7 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS
  • CVE-2021-43980: 2.36% estimated exploitation activity in the next 30 days; percentile 83.80 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

The simplified implementation of blocking reads and writes introduced in Tomcat 10 and back-ported to Tomcat 9.0.47 onwards exposed a long standing (but extremely hard to trigger) concurrency bug in Apache Tomcat 10.1.0 to 10.1.0-M12, 10.0.0-M1 to 10.0.18, 9.0.0-M1 to 9.0.60 and 8.5.0 to 8.5.77 that could cause client connections to share an Http11Processor instance resulting in responses, or part responses, to be received by the wrong client.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-jx7c-7mj5-9438

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2021-43980

Advisory: Apache Tomcat Race Condition vulnerability
IDs: CVE-2021-43980, GHSA-jx7c-7mj5-9438
Record: https://patchnext.com/advisories/cve-2021-43980 (revision 1, source checked 26 Oct 2026, 16:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.apache.tomcat:tomcat 10.1.0-M14, 10.0.20, 9.0.62, 8.5.78. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.apache.tomcat:tomcat: affected >= 8.5.0, < 8.5.78; >= 9.0.0-M1, < 9.0.62; >= 10.0.0-M1, < 10.0.20; >= 10.1.0-M1, < 10.1.0-M14; fixed in 10.1.0-M14, 10.0.20, 8.5.78, 9.0.62

## Suggested inspection (read-only)
- Maven org.apache.tomcat:tomcat: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.apache.tomcat:tomcat.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-jx7c-7mj5-9438 (GitHub-reviewed advisory GHSA-jx7c-7mj5-9438 lists affected ranges: Maven org.apache.tomcat:tomcat >=8.5.0 =9.0.0-M1 =10.0.0-M1 =10.1.0-M1 <10.1.0-M14)

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