CVE-2026-33758: OpenBao has Reflected XSS in its OIDC authentication error message

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 38: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 38% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Only applies if your dependency tree includes github.com/openbao/openbao (Go) < 0.0.0-20260325133417-6e2b2dd84f0e, fixed in 0.0.0-20260325133417-6e2b2dd84f0e. Check your lockfile, including transitive dependencies.

What it is

OpenBao is an open source identity-based secrets management system. Prior to version 2.5.2, OpenBao installations that have an OIDC/JWT authentication method enabled and a role with callbackmode=direct configured are vulnerable to XSS via the errordescription parameter on the page for a failed authentication. This allows an attacker access to the token used in the Web UI by a victim. The errordescription parameter has been replaced with a static error message in v2.5.2. The vulnerability can be mitigated by removing any roles with callbackmode set to direct.

From the GitHub advisory

Impact

OpenBao installations that have an OIDC/JWT authentication method enabled and a role with callbackmode=direct configured are vulnerable to XSS via the errordescription 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 errordescription parameter has been replaced with a static error message in v2.5.2

Workarounds The vulnerability can be mitigated by removing any roles with callbackmode set to direct.

Weakness type: CWE-20, CWE-79, CWE-116, CWE-80.

Product: github.com/openbao/openbao (Go) · Assigned by: GitHub_M · Published: 2026-03-27

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: passive

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.45% probability of exploitation activity in the next 30 days; percentile 38.

Timeline

• 2026-03-26 — GitHub-reviewed advisory GHSA-cpj3-3r2f-xj59 published (critical)
• 2026-03-27 — CVE record published by GitHub_M
• 2026-07-15 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-cpj3-3r2f-xj59 github.com
2. CVE.org record CVE-2026-33758 cve.org
3. NVD entry CVE-2026-33758 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. access.redhat.com access.redhat.com
6. RHBZ#2452294 bugzilla.redhat.com
7. security.access.redhat.com security.access.redhat.com

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