Security readout for executives and security teams
Plain-English summary
This is a critical OpenBao Web UI issue. In specific OIDC/JWT login configurations, a malicious authentication error message can execute in a victim’s browser and expose the Web UI token. Because OpenBao manages secrets, token theft could lead to high business impact.
Executive priority
Treat as urgent for any OpenBao deployment that protects production secrets. The affected configuration is specific, but the consequence is serious because a stolen Web UI token may expose or alter sensitive secret-management data.
Technical view
OpenBao before 2.5.2 is vulnerable to reflected XSS on failed OIDC/JWT authentication when a role uses callback_mode=direct. The error_description parameter was reflected into the failed authentication page. Version 2.5.2 replaces it with a static error message.
Likely exposure
Exposure is limited to OpenBao installations earlier than 2.5.2 with OIDC/JWT authentication enabled and at least one role configured with callback_mode=direct. Installations without that auth flow or role setting are not identified as affected in the bundle.
Exploitation context
The bundle does not show KEV listing or confirmed active exploitation. Exploitation requires victim interaction with the affected authentication error flow. Successful abuse could expose the victim’s Web UI token, creating confidentiality and integrity risk.
Researcher notes
The advisory maps the issue to improper output encoding/input handling and XSS weaknesses. The vulnerable surface is the failed OIDC/JWT authentication page in direct callback mode. The documented fix replaces attacker-influenced error text with a static message.
Mitigation direction
- Upgrade OpenBao to version 2.5.2 or later.
- Remove roles configured with callback_mode=direct where upgrade is not immediate.
- Check OpenBao vendor guidance for any additional operational mitigations.
- Prioritize environments where administrators use the Web UI.
Validation and detection
- Inventory OpenBao versions across all environments.
- Identify OIDC/JWT auth methods enabled in OpenBao.
- Review auth roles for callback_mode=direct.
- Confirm failed authentication pages no longer reflect user-controlled error descriptions.
- Verify remediation against the OpenBao 2.5.2 release or vendor advisory.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-116: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-33758 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L2.86redhat-SADPCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H——GitHub_MVulnerability scoring details
Base CVSS 4.0 score
9.4CriticalVector: 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
Base CVSS 3.1 score
9.6CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-03-27T15:03:38.602Z: Reported to Red Hat.
- 2026-03-27T14:12:33.941Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/openbao/openbao/security/advisories/GHSA-cpj3-3r2f-xj59CVE reference, GitHub_M · x_refsource_CONFIRM
- https://github.com/openbao/openbao/pull/2709CVE reference, GitHub_M · x_refsource_MISC
- https://github.com/openbao/openbao/commit/6e2b2dd84f0e47cebc90d6e79609dd5274732662CVE reference, GitHub_M · x_refsource_MISC
- https://github.com/openbao/openbao/releases/tag/v2.5.2CVE reference, GitHub_M · x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-33758CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2452294CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33758.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.