Is CVE-2021-31921 actively exploited?

No active exploitation of CVE-2021-31921 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-31921 be exploited remotely?

Yes. CVE-2021-31921 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-31921?

CVE-2021-31921 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2021-31921

CWE-862Published: June 2, 2021· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official Description

Istio before 1.8.6 and 1.9.x before 1.9.5 contains a remotely exploitable vulnerability where an external client can access unexpected services in the cluster, bypassing authorization checks, when a gateway is configured with AUTO_PASSTHROUGH routing configuration.

NVD Source

Technical Analysis

CVE-2021-31921 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.