CVE-2026-66273: Apache Qpid Proton-J: Type size/count handling can lead to excessive allocation pre-authentication

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-05 · updated 2026-10-24
Weakness: CWE-789

Description

A pre-authentication attacker could leverage type size/count handling to cause excessive allocation leading to potential denial of service. This issue affects Apache Qpid Proton-J: through 0.34.1. Users are recommended to upgrade to version 0.35.0, which fixes the issue.

Affected products

Apache Software Foundation Apache Qpid Proton-J: before 0.35.0 — fixed in 0.35.0

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache Qpid Proton-J 0.35.0. Check the vendor advisory for mitigations.

References

https://lists.apache.org/thread/z34s9v5w05qk4qqtz5fs3v9wpxz6fnbh
http://www.openwall.com/lists/oss-security/2026/08/04/9

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