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CVE-2021-31920

Istio Authorization Bypass Vulnerability

6.5 Medium

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

1.32%Up 0.9 points since May 27, 2021
90%50%10%1%

What each source reports

NVD Score used 6.5

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

Record
CVE-2021-31920
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CVSS 2.0
4.0 MediumAV:N/AC:L/Au:S/C:P/I:N/A:N
Weakness
CWE-706
Updated
2026-11-02
CVE List No score

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

Record
CVE-2021-31920
Updated
2026-11-02
EUVDEUVD-2022-2845 No score

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

Record
EUVD-2022-2845
Updated
2026-11-03
GitHub AdvisoriesGHSA-6q5m-22mq-q2xv 6.5

Istio Authorization Bypass Vulnerability

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

Record
GHSA-6q5m-22mq-q2xv
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-863
Updated
2026-11-02
OSV 6.5

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

Record
CVE-2021-31920
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVGHSA-6q5m-22mq-q2xv 6.5

Istio Authorization Bypass Vulnerability

Istio before 1.8.6 and 1.9.x before 1.9.5 has a remotely exploitable vulnerability where an HTTP request path with multiple slashes or escaped slash characters (%2F or %5C) could potentially bypass an Istio authorization policy when path based authorization rules are used.

Record
GHSA-6q5m-22mq-q2xv
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-863
Updated
2026-11-02
OSVRHSA-2021:1538 8.3

Red Hat Security Advisory: Red Hat OpenShift Service Mesh 2.0.4 security update

Record
RHSA-2021:1538
CVSS 3.1
8.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Updated
2026-11-02
OSVRHSA-2021:1540 8.3

Red Hat Security Advisory: Red Hat OpenShift Service Mesh 1.1.14 security update

Record
RHSA-2021:1540
CVSS 3.1
8.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
servicemesh-operator
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-3.el8
0:2.0.4-3.el8
servicemesh-proxy
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-1.el8
0:2.0.4-1.el8
servicemesh
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-1.el8
0:2.0.4-1.el8
servicemesh-istioctl
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-1.el8
0:2.0.4-1.el8
servicemesh-mixc
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-1.el8
0:2.0.4-1.el8
servicemesh-mixs
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-1.el8
0:2.0.4-1.el8
servicemesh-pilot-agent
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-1.el8
0:2.0.4-1.el8
servicemesh-pilot-discovery
Red Hat:service_mesh:2.0::el8
From an advisory covering 2 CVEs
 before 0:2.0.4-1.el8
0:2.0.4-1.el8
servicemesh-proxy
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
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Affected packages
PackageAffectedFixed
servicemesh-citadel
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh-galley
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh-istioctl
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh-mixc
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh-mixs
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh-pilot-agent
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh-pilot-discovery
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8
servicemesh-sidecar-injector
Red Hat:service_mesh:1.1::el8
From an advisory covering 2 CVEs
 before 0:1.1.14-1.el8
0:1.1.14-1.el8

History

History
RecordedChangedSources
affected, facts
affected
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-31920 is a medium vulnerability (CVSS 6.5) in Istio, published May 27, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.32%, the 70th percentile. No source names a fixed version.

References

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