CVE-2026-37977

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 83% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: None knownExposed: 0

A fix is available — apply it.

A flaw was found in Keycloak. A remote attacker can exploit a Cross-Origin Resource Sharing (CORS) header injection vulnerability in Keycloak's User-Managed Access (UMA) token endpoint. This flaw occurs because the azp claim from a client-supplied JSON Web Token (JWT) is used to set the Access-Control-Allow-Origin header before the JWT signature is validated. When a specially crafted JWT with an attacker-controlled azp value is processed, this value is reflected as the CORS origin, even if the grant is later rejected. This can lead to the exposure of low-sensitivity information from authorization server error responses, weakening origin isolation, but only when a target client is misconfigured with webOrigins: ["*"].

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
24(Track)
EG Risk 24/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
16%
KEV
Not listed

Published

April 6, 2026

Last Modified

June 26, 2026

Advisory Details (4)

Auto-updated Jun 26, 2026
Patch available. Sources: redhat.
redhat

2455324 – (CVE-2026-37977) CVE-2026-37977 keycloak: org.keycloak.protocol.oidc.grants.ciba: Keycloak: Information disclosure via CORS header injection due to unvalidated JWT azp claim

https://bugzilla.redhat.com/show_bug.cgi?id=2455324
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-37977
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:25098
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:25097

Vendor Advisories for CVE-2026-37977(5)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatrhbk/keycloak-rhel9-operator:26.4-192026-06-25redhat
redhatrhbk/keycloak-rhel92026-06-25redhat
redhatrhbk/keycloak-rhel9-operator:26.6-62026-06-10redhat
mavenorg.keycloak:keycloak-services—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.keycloak:keycloak-services26.5.0 ... 26.6.2 (11 versions)26.6.3—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 5× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 146 total refreshes for this CVE.

  1. 2026-08-25 13:49 UTCEPSS rescore
  2. 2026-08-23 00:19 UTCEPSS rescore
  3. 2026-08-21 23:49 UTCEPSS rescore
  4. 2026-08-20 22:55 UTCEPSS rescore
  5. 2026-08-19 17:03 UTCEPSS rescore
  6. 2026-08-18 13:48 UTCEPSS rescore
  7. 2026-08-17 13:47 UTCEPSS rescore
  8. 2026-08-16 14:56 UTCEPSS rescore
  9. 2026-08-16 08:26 UTCEG score recompute
  10. 2026-08-16 08:26 UTCVendor advisory
  11. 2026-08-16 02:14 UTCEPSS rescore
  12. 2026-08-15 01:30 UTCEPSS rescore
  13. 2026-08-14 05:35 UTCEG score recompute
  14. 2026-08-14 05:35 UTCVendor advisory
  15. 2026-08-13 22:00 UTCEPSS rescore
  16. 2026-08-13 00:33 UTCEG score recompute
  17. 2026-08-13 00:33 UTCVendor advisory
  18. 2026-08-12 13:51 UTCEPSS rescore
  19. 2026-08-12 01:56 UTCEG score recompute
  20. 2026-08-12 01:56 UTCVendor advisory
  21. 2026-08-11 13:43 UTCEPSS rescore
  22. 2026-08-11 03:19 UTCEG score recompute
  23. 2026-08-11 03:19 UTCVendor advisory
  24. 2026-08-11 00:00 UTCEPSS rescore
  25. 2026-08-10 03:42 UTCEG score recompute
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  1. 2026-08-10 03:42 UTCVendor advisory
  2. 2026-08-09 13:46 UTCEPSS rescore
  3. 2026-08-09 05:05 UTCEG score recompute
  4. 2026-08-09 05:05 UTCVendor advisory
  5. 2026-08-08 16:37 UTCEPSS rescore
  6. 2026-08-07 15:11 UTCEG score recompute
  7. 2026-08-07 15:11 UTCVendor advisory
  8. 2026-08-06 13:46 UTCEPSS rescore
  9. 2026-08-06 00:10 UTCEG score recompute
  10. 2026-08-06 00:10 UTCVendor advisory
  11. 2026-08-05 19:17 UTCEPSS rescore
  12. 2026-08-04 15:10 UTCEPSS rescore
  13. 2026-08-04 10:38 UTCEPSS rescore
  14. 2026-08-03 22:30 UTCEG score recompute
  15. 2026-08-03 22:30 UTCVendor advisory
  16. 2026-08-03 10:36 UTCEPSS rescore
  17. 2026-08-02 14:27 UTCEG score recompute
  18. 2026-08-02 14:27 UTCVendor advisory
  19. 2026-08-02 02:27 UTCEPSS rescore
  20. 2026-08-01 04:16 UTCEPSS rescore
  21. 2026-07-30 16:28 UTCEPSS rescore
  22. 2026-07-30 01:30 UTCEPSS rescore
  23. 2026-07-27 14:13 UTCEPSS rescore
  24. 2026-07-26 14:54 UTCEPSS rescore
  25. 2026-07-26 14:54 UTCEPSS rescore
  26. 2026-07-25 14:18 UTCEPSS rescore
  27. 2026-07-25 14:18 UTCEPSS rescore
  28. 2026-07-24 14:17 UTCEPSS rescore
  29. 2026-07-24 14:17 UTCEPSS rescore
  30. 2026-07-23 14:18 UTCEPSS rescore
  31. 2026-07-23 14:18 UTCEPSS rescore
  32. 2026-07-23 03:10 UTCEG score recompute▲ 1.60
  33. 2026-07-22 14:08 UTCEPSS rescore
  34. 2026-07-21 15:24 UTCEPSS rescore
  35. 2026-07-20 17:08 UTCEPSS rescore
  36. 2026-07-19 14:31 UTCEPSS rescore
  37. 2026-07-19 02:29 UTCEPSS rescore
  38. 2026-07-18 10:04 UTCEPSS rescore
  39. 2026-07-16 17:03 UTCEPSS rescore
  40. 2026-07-15 16:57 UTCEPSS rescore
  41. 2026-07-15 16:57 UTCEPSS rescore
  42. 2026-07-15 02:00 UTCEPSS rescore
  43. 2026-07-13 22:30 UTCEPSS rescore
  44. 2026-07-13 06:13 UTCEPSS rescore
  45. 2026-07-13 06:13 UTCEPSS rescore
  46. 2026-07-12 05:46 UTCEPSS rescore
  47. 2026-07-11 08:27 UTCEPSS rescore
  48. 2026-07-09 19:10 UTCEPSS rescore
  49. 2026-07-08 15:15 UTCEPSS rescore
  50. 2026-07-07 13:46 UTCEPSS rescore
  51. 2026-07-06 16:27 UTCEPSS rescore
  52. 2026-07-06 16:27 UTCEPSS rescore
  53. 2026-07-06 02:23 UTCEPSS rescore
  54. 2026-07-06 02:23 UTCEPSS rescore
  55. 2026-07-05 02:30 UTCEPSS rescore
  56. 2026-07-04 06:31 UTCEPSS rescore
  57. 2026-07-01 15:06 UTCEPSS rescore
  58. 2026-06-30 23:22 UTCEPSS rescore
  59. 2026-06-29 14:06 UTCEPSS rescore
  60. 2026-06-28 14:07 UTCEPSS rescore
  61. 2026-06-28 04:56 UTCEPSS rescore
  62. 2026-06-27 03:08 UTCEPSS rescore
  63. 2026-06-25 13:49 UTCEPSS rescore
  64. 2026-06-25 13:49 UTCEPSS rescore
  65. 2026-06-24 14:05 UTCEPSS rescore
  66. 2026-06-23 21:33 UTCEPSS rescore
  67. 2026-06-22 14:25 UTCEPSS rescore
  68. 2026-06-22 14:25 UTCEPSS rescore
  69. 2026-06-21 14:56 UTCEPSS rescore
  70. 2026-06-21 14:56 UTCEPSS rescore
  71. 2026-06-21 01:59 UTCEPSS rescore
  72. 2026-06-19 19:25 UTCEPSS rescore
  73. 2026-06-19 19:25 UTCEPSS rescore
  74. 2026-06-18 17:52 UTCEPSS rescore
  75. 2026-06-18 17:52 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-37977?
CVE-2026-37977 is a medium vulnerability published on April 6, 2026. A flaw was found in Keycloak. A remote attacker can exploit a Cross-Origin Resource Sharing (CORS) header injection vulnerability in Keycloak's User-Managed Access (UMA) token endpoint. This flaw occurs because the azp claim from a client-supplied JSON Web Token (JWT) is used to set the…
When was CVE-2026-37977 disclosed?
CVE-2026-37977 was first published in the National Vulnerability Database on April 6, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-37977 actively exploited?
CVE-2026-37977 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 83.5% of all scored CVEs.
What is the CVSS score of CVE-2026-37977?
CVE-2026-37977 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-37977?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-37977, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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