---
id: CVE-2025-53114
aliases:
  - GHSA-cqgj-h8vf-4w59
title: Acknowledgement extension out of memory
summary: Acknowledgement extension out of memory
severity: high
cvss: 7.5
cwe:
  - CWE-400
vendor: cometd
product: 'org.cometd.java:cometd-java-server-common'
ecosystem: maven
affected:
  - 'org.cometd.java:cometd-java-server-common >= 5.0.0, <= 5.0.22'
  - 'org.cometd.java:cometd-java-server-common >= 6.0.0, <= 6.0.18'
  - 'org.cometd.java:cometd-java-server-common >= 7.0.0, <= 7.0.18'
  - 'org.cometd.java:cometd-java-server-common >= 8.0.0, <= 8.0.8'
patched:
  - 'org.cometd.java:cometd-java-server-common 5.0.23'
  - 'org.cometd.java:cometd-java-server-common 6.0.19'
  - 'org.cometd.java:cometd-java-server-common 7.0.19'
  - 'org.cometd.java:cometd-java-server-common 8.0.9'
published: '2026-06-10'
updated: '2026-06-10'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-cqgj-h8vf-4w59'
references:
  - url: 'https://github.com/cometd/cometd/security/advisories/GHSA-cqgj-h8vf-4w59'
  - url: 'https://github.com/cometd/cometd/issues/2117'
  - url: 'https://github.com/cometd/cometd/pull/2118'
  - url: 'https://github.com/cometd/cometd/pull/2168'
  - url: 'https://github.com/cometd/cometd/pull/2169'
  - url: 'https://github.com/cometd/cometd/discussions/2116'
  - url: 'https://github.com/advisories/GHSA-cqgj-h8vf-4w59'
tags:
  - ghsa
  - maven
epss: 0.00684
epssPercentile: 0.5045
ingestedAt: '2026-07-07T15:41:59.561Z'
---

## Overview

### Impact
Bad clients that always send a fixed batch value while the server is using the acknowledgement extension can cause the unacknowledged message queue to grow indefinitely, eventually resulting in an OutOfMemoryError.

Such bad clients would always send:

```json
{
  "channel": "/meta/connect",
  ...
  "ext": { "ack": 1 }
}
```

The server would never clear the unacknowledged message queue, and one bad client can cause a server outage.

### Patches
5.0.x - https://github.com/cometd/cometd/pull/2168
6.0.x - https://github.com/cometd/cometd/pull/2169
8.0.x - https://github.com/cometd/cometd/pull/2118

### Workarounds
Disable the acknowledgement extension.

### Resources
https://github.com/cometd/cometd/discussions/2116
https://github.com/cometd/cometd/issues/2117

## Affected packages

- `org.cometd.java:cometd-java-server-common >= 5.0.0, <= 5.0.22`
- `org.cometd.java:cometd-java-server-common >= 6.0.0, <= 6.0.18`
- `org.cometd.java:cometd-java-server-common >= 7.0.0, <= 7.0.18`
- `org.cometd.java:cometd-java-server-common >= 8.0.0, <= 8.0.8`

## Remediation

Upgrade to a patched release:

- `org.cometd.java:cometd-java-server-common 5.0.23`
- `org.cometd.java:cometd-java-server-common 6.0.19`
- `org.cometd.java:cometd-java-server-common 7.0.19`
- `org.cometd.java:cometd-java-server-common 8.0.9`