Login Request a demo
High severity · published Sep 23, 2026
CVE-2026-77762
Apache Tomcat: Stale HPACK emitter injects trailers into recycled pooled Request
8.1
CVSS
0.5%
EPSS
No
On KEV
Description
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in Apache Tomcat allows an attacker to inject trailer fields into another HTTP/2 request. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.39 through 9.0.121. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.59 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.26, 10.1.60, 9.0.122, which fix the issue.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 40% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TO
Tomcat · Apache
11.0.0-M1 through 11.0.25; 10.1.0-M1 through 10.1.59; 9.0.39 through 9.0.121; 8.5.59 through 8.5.100 · source: vendor
Affected product
TO
Tomcat
Apache
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77762
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-77762
vendor-advisory
https://lists.apache.org/thread/y5r9fvjo7ol24mkoyoc0st8bqrfyqcyn
More from Tomcat
9.8
CVE-2025-24813
Apache Tomcat: Potential RCE and/or information disclosure and/or information corruption with partial PUT
9.8
CVE-2020-1938
Apache Tomcat Improper Privilege Management Vulnerability
9.8
CVE-2016-8735
Remote code execution is possible with Apache Tomcat before 6.0.48, 7.x before 7.0.73, 8.x before 8.0.39, 8.5.x before 8.5.7, and 9.x before 9.0.0.M12 if…
8.1
CVE-2017-12617
When running Apache Tomcat versions 9.0.0.M1 to 9.0.0, 8.5.0 to 8.5.22, 8.0.0.RC1 to 8.0.46 and 7.0.0 to 7.0.81 with HTTP PUTs enabled (e.g
8.1
CVE-2017-12615
When running Apache Tomcat 7.0.0 to 7.0.79 on Windows with HTTP PUTs enabled (e.g