CVE-2021-39156
Fragments in Path May Lead to Authorization Policy Bypass
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Fragments in Path May Lead to Authorization Policy Bypass
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.
- Record
CVE-2021-39156- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-863
- Updated
- 2026-11-02
EUVDEUVD-2021-1754
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.
- Record
EUVD-2021-1754- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-hqxw-mm44-gc4r
Istio Fragments in Path May Lead to Authorization Policy Bypass
Impact
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
- Istio 1.11.1 and above
- Istio 1.10.4 and above
- Istio 1.9.8 and above
Workarounds
A Lua filter may be written to normalize the path. This is similar to the Path normalization presented in the Security Best Practices guide.
References
More details can be found in the Istio Security Bulletin
For more information
If you have any questions or comments about this advisory, please email us at [email protected]
- Record
GHSA-hqxw-mm44-gc4r- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-706, CWE-863
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2021-39156- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:P/I:N/A:N - Weakness
- CWE-863, CWE-706
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-39156- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
OSVGHSA-hqxw-mm44-gc4r
Istio Fragments in Path May Lead to Authorization Policy Bypass
Impact
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
- Istio 1.11.1 and above
- Istio 1.10.4 and above
- Istio 1.9.8 and above
Workarounds
A Lua filter may be written to normalize the path. This is similar to the Path normalization presented in the Security Best Practices guide.
References
More details can be found in the Istio Security Bulletin
For more information
If you have any questions or comments about this advisory, please email us at [email protected]
- Record
GHSA-hqxw-mm44-gc4r- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-706, CWE-863
- Updated
- 2026-11-02
OSVRHSA-2021:3272
Red Hat Security Advisory: Red Hat OpenShift Service Mesh 2.0.7.1 security update
- Record
RHSA-2021:3272- CVSS 3.1
- 8.3 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L - Updated
- 2026-11-02
OSVRHSA-2021:3273
Red Hat Security Advisory: Red Hat OpenShift Service Mesh 1.1.17.1 security update
- Record
RHSA-2021:3273- CVSS 3.1
- 8.3 High
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
istio.io/istioGo |
before 1.9.8 | 1.9.8 |
istio.io/istioGo |
1.10.0 up to 1.10.4 | 1.10.4 |
istio.io/istioGo |
1.11.0 to 1.11.0 | 1.11.1 |
istio.io/istioGo |
1.11.0 up to 1.11.1 | 1.11.1 |
servicemesh-proxyRed Hat:service_mesh:2.0::el8 From an advisory covering 5 CVEs |
before 0:2.0.7-3.el8 | 0:2.0.7-3.el8 |
servicemeshRed Hat:service_mesh:2.0::el8 From an advisory covering 5 CVEs |
before 0:2.0.7-3.el8 | 0:2.0.7-3.el8 |
servicemesh-istioctlRed Hat:service_mesh:2.0::el8 From an advisory covering 5 CVEs |
before 0:2.0.7-3.el8 | 0:2.0.7-3.el8 |
servicemesh-mixcRed Hat:service_mesh:2.0::el8 From an advisory covering 5 CVEs |
before 0:2.0.7-3.el8 | 0:2.0.7-3.el8 |
servicemesh-mixsRed Hat:service_mesh:2.0::el8 From an advisory covering 5 CVEs |
before 0:2.0.7-3.el8 | 0:2.0.7-3.el8 |
servicemesh-pilot-agentRed Hat:service_mesh:2.0::el8 From an advisory covering 5 CVEs |
before 0:2.0.7-3.el8 | 0:2.0.7-3.el8 |
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| Package | Affected | Fixed |
|---|---|---|
servicemesh-pilot-discoveryRed Hat:service_mesh:2.0::el8 From an advisory covering 5 CVEs |
before 0:2.0.7-3.el8 | 0:2.0.7-3.el8 |
servicemesh-proxyRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-2.el8 | 0:1.1.17-2.el8 |
servicemeshRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-citadelRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-galleyRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-istioctlRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-mixcRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-mixsRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-pilot-agentRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-pilot-discoveryRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
servicemesh-sidecar-injectorRed Hat:service_mesh:1.1::el8 From an advisory covering 5 CVEs |
before 0:1.1.17-3.el8 | 0:1.1.17-3.el8 |
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| PoC in GitHub | mostafaanouarghorab/MicroserviceCVE-2021-39156 | 2026-03-26 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV, PoC in GitHub |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-39156 is a high vulnerability (CVSS 8.1) in Istio, published August 24, 2021. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 1.18%, the 67th percentile. Fixed in istio.io/istio 1.9.8.
References
github.com/istio/istio/security/advisories/GHSA-hqxw-mm44-gc4r
istio.io/latest/news/security/istio-security-2021-008
nvd.nist.gov/vuln/detail/CVE-2021-39156
access.redhat.com/errata/RHSA-2021:3272
Show 23 moreShow less
bugzilla.redhat.com/show_bug.cgi?id=1996915
security.access.redhat.com/data/csaf/v2/advisories/2021/rhsa-2021_3272.json
cve.org/CVERecord?id=CVE-2021-32777