How severe is CVE-2026-66257?

CVE-2026-66257 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-66257 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-66257?

CVE-2026-66257 affects Apache Qpid Proton-j. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-66257?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-66257 published?

CVE-2026-66257 was published on 2026-08-05 and last updated on 2026-08-07.

CVE-2026-66257

CVE-2026-66257 is a high-severity vulnerability in Apache Qpid Proton-j with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (36th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-770
Affected product: Apache Qpid Proton-j
Published: 2026-08-05
Last modified: 2026-08-07

Description

A pre-authentication attacker could leverage unbounded symbol value caching to cause resource exhaustion 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.

Frequently asked questions

What is CVE-2026-66257?: A pre-authentication attacker could leverage unbounded symbol value caching to cause resource exhaustion 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.
How severe is CVE-2026-66257?: CVE-2026-66257 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-66257 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-66257?: CVE-2026-66257 affects Apache Qpid Proton-j. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-66257?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-66257 published?: CVE-2026-66257 was published on 2026-08-05 and last updated on 2026-08-07.

References

Affected products (1)

cpe:2.3:a:apache:qpid_proton-j:*:*:*:*:*:*:*:*

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