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7.5High

Apache Tomcat

CVE-2021-25122

When responding to new h2c connection requests, Apache Tomcat versions 10.0.0-M1 to 10.0.0, 9.0.0.M1 to 9.0.41 and 8.5.0 to 8.5.61 could duplicate request headers and a limited amount of request body from one request to another meaning user A and user B could both see the results of user A's request.

What this means for your business

  • It affects Apache Tomcat. It matters if your company, or a supplier that handles your data, runs it.
  • An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
  • FIRST's prediction model gives it a 18% chance of attack attempts being seen in the next 30 days, ranking above 97% of all known flaws.

What to do

  1. 1Check whether your company or your suppliers run Apache Tomcat, and which version. The affected versions are listed further down this page.
  2. 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

Check if you’re exposedBook a call

Scoring

CVSS
7.5 (v3.1)
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-200
Assigned by
security@apache.org

Dates

Published
2021-03-01
Last modified
2026-08-25
Sources
NVD

Affected products

  • Apache Tomcat8.5.0 - 8.5.61, 9.0.0 - 9.0.41, 9.0.0, 10.0.0
  • Debian Debian Linux9.0, 10.0
  • Oracle Agile Product Lifecycle Management9.3.3, 9.3.6
  • Oracle Communications Cloud Native Core Policy1.14.0
  • Oracle Communications Cloud Native Core Security Edge Protection Proxy1.6.0
  • Oracle Communications Instant Messaging Server10.0.1.5.0
  • Oracle Database12.2.0.1, 19c, 21c
  • Oracle Graph Server And Client- 21.3.0, 21.3.0
  • Oracle Instantis Enterprisetrack17.1, 17.2, 17.3
  • Oracle Managed File Transfer12.2.1.3.0, 12.2.1.4.0
  • Oracle Mysql Enterprise Monitor- 8.0.23
  • Oracle Siebel Ui Framework- 21.9

As listed in the NVD configuration data. Not a statement about your estate.

References