TI-2026-24391 Aliases CVE-2026-31838

Incorrect authorization in istio

LOW 36CWE-863Published 2026-03-10 · Updated 2026-04-07

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Security bypass
Confidentiality · integrity · availability: Low · None · None
Fix status: Partial Red Hat: 7 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-863.

Summary

Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a vulnerability in Envoy RBAC header matching could allow authorization policy bypass when policies rely on HTTP headers that may contain multiple values. An attacker could craft requests with multiple header values in a way that causes Envoy to evaluate the header differently than intended, potentially bypassing authorization checks. This may allow unauthorized requests to reach protected services when policies depend on such header-based matching conditions. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00251 16th percentileScored 2026-11-07

Fix Partial istio (istio): 1.29.1, 1.28.5, 1.27.8Red Hat: 7 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
istio	istio	1.29.0-alpha.0 to before 1.29.1; 1.28.0-alpha.0 to before 1.28.5; before 1.27.8	1.29.1, 1.28.5, 1.27.8	Patch available	CNA

istio Vendoristio Affected 1.29.0-alpha.0 to before 1.29.1; 1.28.0-alpha.0 to before 1.28.5; before 1.27.8 Fixed in 1.29.1, 1.28.5, 1.27.8 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:istio:istio::::::::	before 1.27.8; 1.28.0 to before 1.28.5; 1.29.0 to before 1.29.1	Vulnerable	istio

cpe:2.3:a:istio:istio:*:*:*:*:*:*:*:* Versions before 1.27.8; 1.28.0 to before 1.28.5; 1.29.0 to before 1.29.1 Vulnerable ·istio

Remediation

Fix · CNA istio (istio) Fixed in 1.29.1, 1.28.5, 1.27.8

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
ExternalDNS Operator	Affected	No fix yet: Fix deferred
OpenShift Serverless	Affected	—
OpenShift Service Mesh 2	Affected	No fix yet: Fix deferred
OpenShift Service Mesh 3	Affected	No fix yet: Fix deferred
Red Hat Connectivity Link 1	Affected	No fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)	Affected	—
cert-manager Operator for Red Hat OpenShift	Affected	No fix yet: Fix deferred

Not affected: 1 product

Red Hat Ansible Automation Platform 2

Timeline

2026-10-02 Threatist record created from CVE-2026-31838

References

Advisory 1

https://github.com/istio/istio/security/advisories/GHSA-974c-2wxh-g4ww

Other 1

https://github.com/istio/istio/commit/004fd6921314a8e2293fd195d91645dcbbff0aa1

TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
TI-2022-06055 Authorization Policy bypass in Istio CVSS 3.1CRITICAL 9.8
TI-2021-11909 Istio before 1.8.6 and 1.9.x before 1.9.5 contains a remotely exploitable vulnerability… CVSS 3.1CRITICAL 9.8
TI-2026-24390 Istio JWKS resolver to prevent private key material from being exposed when JWKS fetch fails. CVSS 4.0HIGH 8.7
TI-2022-13090 Ill-formed headers may lead to unexpected behavior in Istio CVSS 3.1CRITICAL 9.8

See all 28 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences