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CVE Record

CVE-2026-0976: Org.keycloak/keycloak-quarkus-server: keycloak: proxy bypass due to improper handling of matrix parameters in url paths

A flaw was found in Keycloak. This improper input validation vulnerability occurs because Keycloak accepts RFC-compliant matrix parameters in URL path segments, while common reverse proxy configurations may ignore or mishandle them. A remote attacker can craft requests to mask path segments, potentially bypassing proxy-level path filtering. This could expose administrative or sensitive endpoints that operators believe are not externally reachable.

LowCVSS 3.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

Keycloak may accept URL path syntax that some reverse proxies mishandle. An attacker could disguise path segments and bypass proxy rules meant to block administrative or sensitive paths. The published severity is low because exploitation depends on specific proxy configurations and only limited confidentiality impact is described.

Executive priority

Treat as a configuration-sensitive low-severity issue. Prioritize review for internet-facing Keycloak deployments and environments relying on reverse proxy path rules to protect admin interfaces.

Technical view

CVE-2026-0976 is an improper input validation issue in keycloak-quarkus-server involving RFC-compliant matrix parameters in URL path segments. If a reverse proxy ignores or normalizes these differently than Keycloak, proxy-level path filtering may be bypassed, potentially exposing endpoints operators intended to keep internal.

Likely exposure

Organizations using affected Red Hat Keycloak-related packages behind reverse proxies with path-based access controls are the likely exposure group. Risk is higher where administrative or sensitive Keycloak paths rely on proxy filtering rather than network isolation and application authorization.

Exploitation context

The source bundle does not show CISA KEV listing or confirmed active exploitation. The CVSS vector indicates network access, no privileges, no user interaction, high attack complexity, and limited confidentiality impact.

Researcher notes

Evidence is limited to the CVE description, Red Hat references, affected package names, and CVSS data. No affected version ranges, fixed versions, patches, or exploitation reports are provided in the source bundle.

Mitigation direction

  • Check Red Hat guidance for affected package status, errata, and supported fixes.
  • Review reverse proxy rules for path filtering around Keycloak administrative or sensitive endpoints.
  • Avoid relying only on proxy path filters to protect Keycloak admin endpoints.
  • Use network restrictions and strong application-level controls for administrative access.
  • Confirm proxy and backend handle matrix parameters consistently.

Validation and detection

  • Inventory Red Hat Build of Keycloak and listed JBoss EAP packages using keycloak-quarkus-server components.
  • Identify deployments where Keycloak is reachable through a reverse proxy.
  • Review proxy configurations for path-based allow or deny rules protecting sensitive Keycloak paths.
  • Test in a controlled environment whether matrix-parameter paths are normalized consistently.
  • Check Red Hat CVE and Bugzilla pages for updated affected versions and fixes.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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

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cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-0976 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Low
CVSS
3.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Official CVE source material

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.

1CVSS vectors
5Timeline events
1ADP providers
3Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
3.7CVSS 3.1LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N2.21.4redhat

Vulnerability scoring details

Base CVSS 3.1 score

3.7Low
CVSS 3.1 vector shape for CVE-2026-0976Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. Source timelineredhat

    Made public.

  2. Source timelineredhat

    Reported to Red Hat.

  3. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Red HatRed Hat Build of Keycloakkeycloak-quarkus-serveraffected
Red HatRed Hat JBoss Enterprise Application Platform 8keycloak-quarkus-serveraffected
Red HatRed Hat JBoss Enterprise Application Platform 8keycloak-quarkus-server-appaffected
Red HatRed Hat JBoss Enterprise Application Platform 8keycloak-quarkus-server-deploymentaffected
Red HatRed Hat JBoss Enterprise Application Platform Expansion Packkeycloak-quarkus-serveraffected
Red HatRed Hat JBoss Enterprise Application Platform Expansion Packkeycloak-quarkus-server-appaffected
Red HatRed Hat JBoss Enterprise Application Platform Expansion Packkeycloak-quarkus-server-deploymentaffected
Weakness

CWE details

CWE-20

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.