CVE-2026-67591: Apache Qpid ProtonJ2: Incoming session flow control window can be exceeded

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% 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-770

Description

An authenticated attacker could exceed the session flow control incoming window potentially leading to denial of service. This issue affects Apache Qpid ProtonJ2: through 1.1.0. Users are recommended to upgrade to version 1.2.0, which fixes the issue.

Affected products

Apache Software Foundation Apache Qpid ProtonJ2: before 1.2.0 — fixed in 1.2.0

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache Qpid ProtonJ2 1.2.0. Check the vendor advisory for mitigations.

References

https://lists.apache.org/thread/rwmggh2bkm6qotxpdfcplht3jgw5n036
http://www.openwall.com/lists/oss-security/2026/08/04/30

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