CVE-2026-66273: A pre-authentication attacker could leverage type size/count handling to cause excessive allocation leading to

Q: How do I fix CVE-2026-66273?

qpid proton-j: upgrade to 0.35.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-66273 being exploited?

CVE-2026-66273 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-66273 affect?

CVE-2026-66273 affects qpid proton-j. Severity is high (CVSS 7.5). 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 versi

Q: How urgent is CVE-2026-66273?

Priority 50/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-66273 is a high-severity flaw (CVSS 7.5) affecting qpid proton-j. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 45%)
CISA exploited list	No
Weakness	CWE-789
Published	2026-08-05
Last modified	2026-10-23

Publisher (CNA): Apache Software Foundation · Vendor: apache

Am I affected?

Timeline

2026-08-05 06:16 UTCPublished CVE record published
2026-10-23 21:10 UTCUpdated Record last modified

apache qpid proton-j UPGRADE

Affected: < 0.35.0

Fixed in: 0.35.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy qpid-proton-j || rpm -q qpid-proton-j || qpid-proton-j --version

2. UPGRADE to 0.35.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade qpid-proton-j

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade qpid-proton-j

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

Fedora 46 · python-streamlink · FIXED · 8.6.2-1.fc46 · FEDORA-2026-a56fcfdc08 · source

sudo dnf upgrade --advisory=FEDORA-2026-a56fcfdc08

Fedora ELN · valgrind · FIXED · 3.28.0-1.eln159 · FEDORA-2026-c593ef1d15 · source

sudo dnf upgrade --advisory=FEDORA-2026-c593ef1d15

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-66273?

qpid proton-j: upgrade to 0.35.0. Exact commands for each OS are on this page.

Is CVE-2026-66273 being exploited?

CVE-2026-66273 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-66273 affect?

CVE-2026-66273 affects qpid proton-j. Severity is high (CVSS 7.5). 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 versi

How urgent is CVE-2026-66273?

Priority 50/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

CVE-2026-66257 HIGH 7.5 UPGRADE A pre-authentication attacker could leverage unbounded symbol value caching to cause resource exhaustion leadi
CVE-2026-66274 HIGH 7.5 UPGRADE A pre-authentication attacker could leverage type nesting to cause a StackOverflowError potentially leading to
CVE-2026-66275 MEDIUM 6.5 UPGRADE An authenticated attacker could exceed the session flow control incoming window potentially leading to denial
CVE-2026-66276 MEDIUM 6.5 UPGRADE An authenticated attacker can craft a disposition frame with large or illegal ranges causing excessive CPU usa
CVE-2026-66277 MEDIUM 6.5 UPGRADE It was not possible to govern the maximum number of transfer frames per incoming delivery, enabling an authent

References

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