CVE-2021-25122: Apache Tomcat h2c request mix-up

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 18.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-01 · updated 2026-10-08
Weakness: CWE-200

Description

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.

Affected products

Apache Tomcat: from 8.5.0 through 8.5.61; from 9.0.0 through 9.0.41; 9.0.0-milestone1, 9.0.0-milestone10, 9.0.0-milestone11, 9.0.0-milestone12, 9.0.0-milestone13, 9.0.0-milestone14 (+28)
Debian Linux: 9.0, 10.0
Oracle Corporation Oracle Agile PLM: 9.3.3, 9.3.6
Oracle Communications Cloud Native Core Policy: 1.14.0
Oracle Communications Cloud Native Core Security Edge Protection Proxy: 1.6.0
Oracle Communications Instant Messaging Server: 10.0.1.5.0
Oracle Database: 12.2.0.1, 19c, 21c
Oracle Graph Server And Client: before 21.3.0; 21.3.0 — fixed in 21.3.0
Oracle Instantis Enterprisetrack: 17.1, 17.2, 17.3
Oracle Corporation Oracle Managed File Transfer: 12.2.1.3.0, 12.2.1.4.0
Oracle Corporation MySQL Enterprise Monitor: through 8.0.23
Oracle Corporation Siebel UI Framework: through 21.9

How to fix

Upgrade to a fixed version: Oracle Graph Server And Client 21.3.0. Check the vendor advisory for mitigations.

References

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