CVE-2021-25122

CVE-2021-25122 is a high-severity vulnerability in Apache Tomcat with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 18% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-200.

Key facts

• Severity: High (CVSS 3.x base score 7.5)
• CVSS v2: 5.0
• EPSS exploit prediction: 18% (97th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-200
• Affected product: Apache Tomcat
• Published: 2021-03-01
• Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.

How severe is CVE-2021-25122?

CVE-2021-25122 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-25122 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 18% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-25122?

CVE-2021-25122 primarily affects Apache Tomcat. In total, 54 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-25122?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-25122 published?

CVE-2021-25122 was published on 2021-03-01 and last updated on 2026-06-17.

References

• http://www.openwall.com/lists/oss-security/2021/03/01/1
• https://lists.apache.org/thread.html/r7b95bc248603360501f18c8eb03bb6001ec0ee3296205b34b07105b7%40%3Cannounce.apache.org%3E
• https://lists.apache.org/thread.html/r7b95bc248603360501f18c8eb03bb6001ec0ee3296205b34b07105b7%40%3Cannounce.tomcat.apache.org%3E
• https://lists.apache.org/thread.html/r7b95bc248603360501f18c8eb03bb6001ec0ee3296205b34b07105b7%40%3Cdev.tomcat.apache.org%3E
• https://lists.apache.org/thread.html/r7b95bc248603360501f18c8eb03bb6001ec0ee3296205b34b07105b7%40%3Cusers.tomcat.apache.org%3E
• https://lists.apache.org/thread.html/rcd90bf36b1877e1310b87ecd14ed7bbb15da52b297efd9f0e7253a3b%40%3Cusers.tomcat.apache.org%3E
• https://lists.apache.org/thread.html/rd0463f9a5cbc02a485404c4b990f0da452e5ac5c237808edba11c947%40%3Cusers.tomcat.apache.org%3E
• https://lists.apache.org/thread.html/rf6d5d57b114678d8898005faef31e9fd6d7c981fcc4ccfc3bc272fc9%40%3Cdev.tomcat.apache.org%3E
• https://lists.debian.org/debian-lts-announce/2021/03/msg00018.html
• https://security.gentoo.org/glsa/202208-34
• https://security.netapp.com/advisory/ntap-20210409-0002/
• https://www.debian.org/security/2021/dsa-4891
• https://www.oracle.com//security-alerts/cpujul2021.html
• https://www.oracle.com/security-alerts/cpujan2022.html
• https://www.oracle.com/security-alerts/cpuoct2021.html

Affected products (54)

• cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone1:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone10:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone11:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone12:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone13:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone14:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone15:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone16:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone17:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone18:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone19:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone2:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone20:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone21:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone22:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone23:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone24:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone25:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone26:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone27:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone3:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone4:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone5:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:-:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone1:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone10:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone2:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone3:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone4:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone5:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone6:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone7:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone8:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone9:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:agile_plm:9.3.3:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:agile_plm:9.3.6:*:*:*:*:*:*:*
• cpe:2.3:a:oracle:communications_cloud_native_core_policy:1.14.0:*:*:*:*:*:*:*

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