How severe is CVE-2026-31837?

CVE-2026-31837 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 high, integrity none, and availability none.

Is CVE-2026-31837 being actively exploited?

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

What products are affected by CVE-2026-31837?

CVE-2026-31837 affects Istio. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-31837?

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.

Does CVE-2026-31837 have an EU (EUVD) identifier?

Yes. CVE-2026-31837 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10938.

When was CVE-2026-31837 published?

CVE-2026-31837 was published on 2026-03-10 and last updated on 2026-06-30.

CVE-2026-31837

CVE-2026-31837 is a high-severity vulnerability in Istio 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-200.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.7
EPSS exploit prediction: 0% (30th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-10938
Weakness: CWE-200
Affected product: Istio
Published: 2026-03-10
Last modified: 2026-06-30

Description

Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a user of Istio is impacted if the JWKS resolver becomes unavailable or the fetch fails, exposing hardcoded defaults regardless of use of the RequestAuthentication resource. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.

Frequently asked questions

What is CVE-2026-31837?: Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a user of Istio is impacted if the JWKS resolver becomes unavailable or the fetch fails, exposing hardcoded defaults regardless of use of the RequestAuthentication resource. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.
How severe is CVE-2026-31837?: CVE-2026-31837 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 high, integrity none, and availability none.
Is CVE-2026-31837 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31837?: CVE-2026-31837 affects Istio. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-31837?: 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.
Does CVE-2026-31837 have an EU (EUVD) identifier?: Yes. CVE-2026-31837 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10938.
When was CVE-2026-31837 published?: CVE-2026-31837 was published on 2026-03-10 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:istio:istio:*:*:*:*:*:*:*:*

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