Priority reviewHigh

CVE-2021-25122

Apache Software Foundation Apache Tomcat, tomcat, debian linux

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.

CVSS
7.5
EPSS
18.1%
97.0% percentile
CISA KEV
Not listed
Published
2021.03.01
PRIORITY ASSESSMENT

Priority review

FIRST EPSS indicates an elevated probability of exploitation.

Known exploitationNot established by KEV
Exploit probability18.1%
Technical severityCVSS 7.5

Vulnerability overview

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 product and versions

Product
Apache Software Foundation Apache Tomcat, tomcat, debian linux
Affected versions
>= Apache Tomcat 10 < 10.0.2, >= Apache Tomcat 9 < 9.0.42, >= Apache Tomcat 8.5 < 8.5.62, >= 8.5.0 <= 8.5.61, >= 9.0.0 <= 9.0.41, 9.0.0, 10.0.0, 9.0, 10.0, 9.3.3, 9.3.6, 1.14.0, 1.6.0, 10.0.1.5.0, 12.2.0.1, 19c, 21c, < 21.3.0, 21.3.0, 17.1
Fixed versions
21.3.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Apache Software Foundation Apache Tomcat, tomcat, debian linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CWE
CWE-200