---
id: CVE-2026-77762
title: >-
  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…
summary: >-
  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…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-362
  - CWE-821
vendor: Apache Software Foundation
product: Apache Tomcat
affected:
  - apache_tomcat >= 11.0.0-M1 <= 11.0.25
  - apache_tomcat >= 10.1.0-M1 <= 10.1.59
  - apache_tomcat >= 9.0.39 <= 9.0.121
  - apache_tomcat >= 8.56.59 <= 8.5.100
patched:
  - hardened_images
published: '2026-09-23'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T15:22:35.070'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-77762'
references:
  - url: 'https://lists.apache.org/thread/y5r9fvjo7ol24mkoyoc0st8bqrfyqcyn'
    label: security@apache.org
  - url: 'http://www.openwall.com/lists/oss-security/2026/09/23/23'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77762.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-77762'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2539353'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-77762'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-77762'
  - url: 'https://access.redhat.com/errata/RHSA-2026:68257'
  - url: 'https://access.redhat.com/errata/RHSA-2026:68258'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00464
epssPercentile: 0.40023
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-23T15:40:01.556894Z'
scores:
  nvd: 8.1
  vendor: 6.5
  adp: 8.1
ingestedAt: '2026-09-23T11:22:32.915Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:68257** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68257)
- **RHSA-2026:68258** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:68258)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat JBoss Web Server 5, … · updated 2026-09-30 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77762.json)