CVE-2026-33758: Github.com/openbao/openbao Cross-Site Scripting Vulnerability

CRITICAL
Advisory Identifier: GHSA-cpj3-3r2f-xj59
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CWE-80 CWE-20
Published
Advisory Summary

CVE-2026-33758 is a CRITICAL cross-site scripting vulnerability (CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)) affecting Github.com/openbao/openbao libraries in the Go ecosystem. The issue involves openbao has reflected xss in its oidc authentication error message. Remediation is available by upgrading affected packages to version 0.0.0-20260325133417-6e2b2dd84f0e.

CVE-2026-33758 at a Glance

CVE Identifier CVE-2026-33758
GHSA Identifier GHSA-cpj3-3r2f-xj59
Severity CRITICAL
CVSS v3.1 Base Score N/A
CWE Classification CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
Affected Product Github.com/openbao/openbao
Package Ecosystem Go
Published Date
Last Updated

How to Fix CVE-2026-33758

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

github.com/openbao/openbao fixed: 0.0.0-20260325133417-6e2b2dd84f0e 
Upgrade github.com/openbao/openbao to 0.0.0-20260325133417-6e2b2dd84f0e
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 github.com/openbao/openbao

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-33758, inspect your project dependencies for Github.com/openbao/openbao:

inspect dependencies for github.com/openbao/openbao

Analyze the terminal output to locate any version of Github.com/openbao/openbao in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.0.0-20260325133417-6e2b2dd84f0e), 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-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS), where the product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. In Github.com/openbao/openbao, 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 OpenBao installations that have an OIDC/JWT authentication method enabled and a role with `callback_mode=direct` configured are vulnerable to XSS via the `error_description` parameter on the page for a failed authentication. This allows an attacker access to the token used in the Web UI by a victim. ### Patches The `error_description` parameter has been replaced with a static error message in v2.5.2 ### Workarounds The vulnerability can be mitigated by removing any roles with `callback_mode` set to `direct`.

CVE-2026-33758 Affected Github.com/openbao/openbao Versions

1 component(s)
Fixed Versions:
0.0.0-20260325133417-6e2b2dd84f0e
Product / Package Ecosystem Affected Versions Fixed Version
github.com/openbao/openbao
golang/github.com/openbao/openbao
Go
< 0.0.0-20260325133417-6e2b2dd84f0e
0.0.0-20260325133417-6e2b2dd84f0e

References

GitHub Advisory / Wiki ADVISORY
https://github.com/openbao/openbao/security/advisories/GHSA-cpj3-3r2f-xj59
NVD — CVE-2026-33758 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33758
Github.com/openbao/openbao Source Repository REPOSITORY
https://github.com/openbao/openbao/pull/2709
Security Fix Commit FIX COMMIT
https://github.com/openbao/openbao/commit/6e2b2dd84f0e47cebc90d6e79609dd5274732662
Github.com/openbao/openbao Source Repository REPOSITORY
https://github.com/openbao/openbao
Github.com/openbao/openbao Release RELEASE
https://github.com/openbao/openbao/releases/tag/v2.5.2

Frequently Asked Questions

What is CVE-2026-33758?
CVE-2026-33758 is a security vulnerability in Github.com/openbao/openbao involving OpenBao has Reflected XSS in its OIDC authentication error message under CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS).
Which Github.com/openbao/openbao versions are affected?
Affected versions include releases prior to 0.0.0-20260325133417-6e2b2dd84f0e across affected packages: github.com/openbao/openbao.
What version fixes CVE-2026-33758?
Upgrading to 0.0.0-20260325133417-6e2b2dd84f0e (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/openbao/openbao affected?
Yes, github.com/openbao/openbao is affected in releases prior to 0.0.0-20260325133417-6e2b2dd84f0e. Upgrade your dependency to 0.0.0-20260325133417-6e2b2dd84f0e or later.
What CWE is associated with CVE-2026-33758?
CVE-2026-33758 is classified under CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) (The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages.).
How can I check Go dependencies for CVE-2026-33758?
Run the dependency tree command: 'inspect dependencies for github.com/openbao/openbao'. 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-cpj3-3r2f-xj59",
  "modified" : "2026-03-27T21:33:53Z",
  "published" : "2026-03-26T18:37:09Z",
  "aliases" : [ "CVE-2026-33758" ],
  "summary" : "OpenBao has Reflected XSS in its OIDC authentication error message",
  "details" : "### Impact\n\nOpenBao installations that have an OIDC/JWT authentication method enabled and a role with `callback_mode=direct` configured are vulnerable to XSS via the  `error_description` parameter on the page for a failed authentication.\n\nThis allows an attacker access to the token used in the Web UI by a victim.\n\n### Patches\nThe `error_description` parameter has been replaced with a static error message in v2.5.2\n\n### Workarounds\nThe vulnerability can be mitigated by removing any roles with `callback_mode` set to `direct`.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/openbao/openbao"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.0.0-20260325133417-6e2b2dd84f0e"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/openbao/openbao/security/advisories/GHSA-cpj3-3r2f-xj59"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33758"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/openbao/openbao/pull/2709"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/openbao/openbao/commit/6e2b2dd84f0e47cebc90d6e79609dd5274732662"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/openbao/openbao"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/openbao/openbao/releases/tag/v2.5.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-80" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-26T18:37:09Z",
    "nvd_published_at" : "2026-03-27T15:16:57Z"
  }
}