CVE-2026-66275 Apache Qpid Proton-J: Incoming session flow control window can be exceeded
An authenticated attacker can exceed the session flow control window in Apache Qpid Proton-J, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-66275?
CVE-2026-66275 is a medium-severity denial of service vulnerability in Apache Qpid Proton-J, published on 5 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
An authenticated attacker could exceed the session flow control incoming window potentially leading to 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.
Weakness: CWE-770
Which versions are affected by CVE-2026-66275?
It affects 1 product.
Products include Apache Qpid Proton-J.
How do I fix CVE-2026-66275?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-66275 being exploited?
There is no known exploitation of CVE-2026-66275 in the wild and no public exploit code.
Other vulnerabilities in Apache Qpid Proton-J
- CVE-2026-66257 Apache Qpid Proton-J: Unbounded symbol value caching can lead to pre-authentication resource exhaustion
- CVE-2026-66273 Apache Qpid Proton-J: Type size/count handling can lead to excessive allocation pre-authentication
- CVE-2026-66274 Apache Qpid Proton-J: Unbounded type nesting can lead to pre-authentication stackoverflow
- CVE-2018-17187 Improper Certificate Validation in proton-j
- CVE-2026-66276 Apache Qpid Proton-J: Unbounded disposition range handling can lead to denial of service
Sources
Also known as CLEANSTART-2026-ZS57953, GHSA-vx3v-mcrw-7985.