Security readout for executives and security teams
Plain-English summary
This Keycloak flaw can let one upstream identity-provider account reuse another session’s email-verification proof and link itself to a victim’s local Keycloak account. That could expose or alter the victim’s account data. Exploitation requires a logged-in attacker and user interaction, so urgency is moderate, not emergency-level.
Executive priority
Treat as a scheduled but important identity-platform update. The issue can affect account ownership and sensitive access, but available evidence does not show active exploitation and exploitation conditions are constrained.
Technical view
In first-broker-login, Keycloak stores cross-session verification proof by local userId and idpAlias, but not the verified upstream identity. A second account on the same IdP can consume that proof and link to the victim’s local account. Red Hat rates it medium, CVSS 6.4, CWE-639, with high confidentiality and integrity impact.
Likely exposure
Exposure is most relevant to Red Hat build of Keycloak 26.4 and 26.6 deployments using brokered identity login and account linking. The source bundle lists specific affected Red Hat Keycloak packages and marks 26.4.13 and 26.6.3 package entries as unaffected.
Exploitation context
No source in the bundle states active exploitation, and CISA KEV is false. The CVSS vector indicates network reachability, high attack complexity, low privileges, and required user interaction. Abuse depends on identity-broker and first-login/account-linking flows.
Researcher notes
Key point is missing binding between verification proof and upstream identity. Validate only in authorized test environments by confirming whether cross-session proof consumption is tied to the exact external identity. Avoid assuming impact outside Red Hat build of Keycloak versions listed in the source bundle.
Mitigation direction
- Review the Red Hat CVE page and linked RHSAs for official remediation guidance.
- Update affected Red Hat build of Keycloak packages to vendor-designated unaffected releases.
- Prioritize realms using identity brokering and first-broker-login account linking.
- Temporarily review or restrict risky account-linking flows if vendor guidance supports it.
Validation and detection
- Inventory Red Hat build of Keycloak versions and package names in production.
- Identify realms configured with external identity providers and first-broker-login flows.
- Check whether installed packages match affected 26.4 or 26.6 entries.
- Confirm remediation against Red Hat advisories RHSA-2026:25097, 25098, 30049, and 30050.
- Review account-linking audit logs for unexpected IdP links to local users.
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-639: 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 lookupCVE-2026-9087 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
- Medium
- CVSS
- 6.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
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
1 official scoreWe 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:H/PR:L/UI:R/S:U/C:H/I:H/A:N1.25.2redhatVulnerability scoring details
Base CVSS 3.1 score
6.4MediumVector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- Source timelineredhat
Reported to Red Hat.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- Source timelineredhat
Made public.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- RHSA-2026:25097CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2026:25098CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2026:30049CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2026:30050CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/security/cve/CVE-2026-9087CVE reference, redhat · vdb-entry, x_refsource_REDHAT
- RHBZ#2480172CVE reference, redhat · issue-tracking, x_refsource_REDHAT
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.
Authorization Bypass Through User-Controlled Key
Authorization Bypass Through User-Controlled Key represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.