CVE-2026-39350: Istio AuthorizationPolicy ServiceAccounts Regex Injection Vulnerability

MODERATE
Advisory Identifier: GHSA-9gcg-w975-3rjh
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CVSS 5.4
CWE-185
Published
Advisory Summary

CVE-2026-39350 is a MODERATE (CVSS 5.4) authorizationpolicy serviceaccounts regex injection vulnerability (CWE-185: Incorrect Regular Expression) affecting Istio libraries in the Go ecosystem. The issue involves authorizationpolicy serviceaccounts regex injection via unescaped dots. Remediation is available by upgrading affected packages to version 0.0.0-20260403004500-692e460c342d.

CVE-2026-39350 at a Glance

CVE Identifier CVE-2026-39350
GHSA Identifier GHSA-9gcg-w975-3rjh
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-185: Incorrect Regular Expression
Affected Product Istio
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 5.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-39350

To remediate this vulnerability, upgrade all affected Istio dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

istio.io/istio fixed: 0.0.0-20260403004500-692e460c342d 
Upgrade istio.io/istio to 0.0.0-20260403004500-692e460c342d
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for istio.io/istio

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-39350, inspect your project dependencies for Istio:

inspect dependencies for istio.io/istio

Analyze the terminal output to locate any version of Istio in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.0.0-20260403004500-692e460c342d), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-185: Incorrect Regular Expression, where the product specifies a regular expression in a way that causes data to be improperly matched or compared. In Istio, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact The `serviceAccounts` and `notServiceAccounts` fields in AuthorizationPolicy incorrectly interpret dots (`.`) as a regular expression matcher. Because `.` is a valid character in a service account name, an `AuthorizationPolicy` ALLOW rule targeting SA e.g. `cert-manager.io` also matches `cert-manager-io`, `cert-managerXio`, etc. A DENY rule targeting the same name fails to block those variants. ### Patches Fixes are available in 1.29.2, 1.28.6, and 1.27.9 ### Workarounds None

CVE-2026-39350 Affected Istio Versions

1 component(s)
Fixed Versions:
0.0.0-20260403004500-692e460c342d
Product / Package Ecosystem Affected Versions Fixed Version
istio.io/istio
golang/istio.io/istio
Go
≥ 0.0.0-20241024090207-0bf27d49ba4b
< 0.0.0-20260403004500-692e460c342d
0.0.0-20260403004500-692e460c342d

References

GitHub Advisory / Wiki ADVISORY
https://github.com/istio/istio/security/advisories/GHSA-9gcg-w975-3rjh
NVD — CVE-2026-39350 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39350
Security Fix Commit FIX COMMIT
https://github.com/istio/istio/commit/692e460c342d8f308a35b6ecbdace47807da8ade
Istio Source Repository REPOSITORY
https://github.com/istio/istio

Frequently Asked Questions

What is CVE-2026-39350?
CVE-2026-39350 is a security vulnerability in Istio involving AuthorizationPolicy serviceAccounts regex injection via unescaped dots under CWE-185: Incorrect Regular Expression.
Which Istio versions are affected?
Affected versions include releases prior to 0.0.0-20260403004500-692e460c342d across affected packages: istio.io/istio.
What version fixes CVE-2026-39350?
Upgrading to 0.0.0-20260403004500-692e460c342d (or the latest patched release for your respective branch) resolves the vulnerability.
Is istio.io/istio affected?
Yes, istio.io/istio is affected in releases prior to 0.0.0-20260403004500-692e460c342d. Upgrade your dependency to 0.0.0-20260403004500-692e460c342d or later.
What is the CVSS score of CVE-2026-39350?
CVE-2026-39350 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2026-39350?
CVE-2026-39350 is classified under CWE-185: Incorrect Regular Expression (The product specifies a regular expression in a way that causes data to be improperly matched or compared.).
How can I check Go dependencies for CVE-2026-39350?
Run the dependency tree command: 'inspect dependencies for istio.io/istio'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9gcg-w975-3rjh",
  "modified" : "2026-04-16T20:44:46Z",
  "published" : "2026-04-16T20:44:46Z",
  "aliases" : [ "CVE-2026-39350" ],
  "summary" : "Istio: AuthorizationPolicy serviceAccounts regex injection via unescaped dots",
  "details" : "### Impact\nThe `serviceAccounts` and `notServiceAccounts` fields in AuthorizationPolicy incorrectly interpret dots (`.`) as a regular expression matcher. Because `.` is a valid character in a service account name, an `AuthorizationPolicy` ALLOW rule targeting SA e.g. `cert-manager.io` also matches `cert-manager-io`, `cert-managerXio`, etc. A DENY rule targeting the same name fails to block those variants.\n\n### Patches\nFixes are available in 1.29.2, 1.28.6, and 1.27.9\n\n### Workarounds\nNone",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "istio.io/istio"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.0.0-20241024090207-0bf27d49ba4b"
      }, {
        "fixed" : "0.0.0-20260403004500-692e460c342d"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/istio/istio/security/advisories/GHSA-9gcg-w975-3rjh"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39350"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/istio/istio/commit/692e460c342d8f308a35b6ecbdace47807da8ade"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/istio/istio"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-185" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-16T20:44:46Z",
    "nvd_published_at" : "2026-04-15T23:16:09Z"
  }
}