CVE-2021-39156

Fragments in Path May Lead to Authorization Policy Bypass

HIGH
7.5
CVSS Score
Published: August 24, 2021 at 10:30 PM UTC
Updated: June 17, 2026 at 04:03 AM UTC
1 product affected across 1 vendorIstio

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Severity
HIGH7.5
Exploit prediction
EPSS 1%

Description

Istio is an open source platform for providing a uniform way to integrate microservices, manage traffic flow across microservices, enforce policies and aggregate telemetry data. Istio 1.11.0, 1.10.3 and below, and 1.9.7 and below contain a remotely exploitable vulnerability where an HTTP request with `#fragment` in the path may bypass Istio’s URI path based authorization policies. Patches are available in Istio 1.11.1, Istio 1.10.4 and Istio 1.9.8. As a work around a Lua filter may be written to normalize the path.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.10.4v < 1.11.1v < 1.9.81.10.0 ≤ v < 1.10.31.11.0 ≤ v < 1.11.1
Affected range stops below 1.10.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.10.4, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.11.1, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.9.8, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-863CWE-706

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