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Fencer Vulns
critical 9.6

CVE-2026-33758 json

OpenBao has Reflected XSS in its OIDC authentication error message

published 2026-03-26 7 mo ago modified 2026-09-08 2 mo ago also BIT-openbao-2026-33758 , EUVD-2026-16626 , GHSA-cpj3-3r2f-xj59 , GO-2026-4862

cvss
9.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

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 `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. The `error_description` parameter has been replaced with a static error message in v2.5.2. The vulnerability can be mitigated by removing any roles with `callback_mode` set to `direct`.

Patch / fix

  • go github.com/openbao/openbao 0.0.0-20260325133417-6e2b2dd84f0e
  • bitnami openbao 2.5.2
  • openbao openbao 2.5.2
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260326T203309-150000.1.155.2

suse advisories SUSE-SU-2026:1135-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
  • openbao openSUSE Tumbleweed 2.5.2-1.1

opensuse advisories openSUSE-SU-2026:21483-1openSUSE-SU-2026:10438-1

  • openbao Alpine 3.24, Alpine 3.23 2.5.4-r0

alpine advisories ALPINE-CVE-2026-33758

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-33758 updated cvss 9.6

OpenBao: reflected XSS in OpenBao OIDC authentication error message

  • Red Hat Cryostat 4 cryostat/cryostat-storage-rhel9
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
7 mo ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 9.4 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
CISA ADP 3.1 9.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L
CNA 4.0 9.4 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CNA 3.1 9.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L

Affected packages

ecosystem package affected fixed in
go github.com/openbao/openbao
<0.0.0-20260325133417-6e2b2dd84f0e
0.0.0-20260325133417-6e2b2dd84f0e
bitnami openbao
<2.5.2
2.5.2

Affected products

  • openbao openbao
  • Red Hat Cryostat 4

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-79 Improper Neutralization of Input During Web Page Generation
  • CWE-116 Improper Encoding or Escaping of Output
  • CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.