CVE-2026-37977

MEDIUMNVD 5.33.7▼
EchelonGraph scoreMEDIUM confidence

Score 3.7 from GitHub Security Advisory (severity: LOW) published 2026-04-06. NVD baseline CVSS 3.7; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
3.7(medium)
EPSS
16.6%
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(4)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
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-services1.0-alpha-1 ... 9.0.3 (224 versions)——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 36× 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.

  1. 2026-07-11 08:27 UTCEPSS rescore
  2. 2026-07-09 19:10 UTCEPSS rescore
  3. 2026-07-08 15:15 UTCEPSS rescore
  4. 2026-07-07 13:46 UTCEPSS rescore
  5. 2026-07-06 16:27 UTCEPSS rescore
  6. 2026-07-06 16:27 UTCEPSS rescore
  7. 2026-07-06 02:23 UTCEPSS rescore
  8. 2026-07-06 02:23 UTCEPSS rescore
  9. 2026-07-05 02:30 UTCEPSS rescore
  10. 2026-07-04 06:31 UTCEPSS rescore
  11. 2026-07-01 15:06 UTCEPSS rescore
  12. 2026-06-30 23:22 UTCEPSS rescore
  13. 2026-06-29 14:06 UTCEPSS rescore
  14. 2026-06-28 14:07 UTCEPSS rescore
  15. 2026-06-28 04:56 UTCEPSS rescore
  16. 2026-06-27 03:08 UTCEPSS rescore
  17. 2026-06-25 13:49 UTCEPSS rescore
  18. 2026-06-25 13:49 UTCEPSS rescore
  19. 2026-06-24 14:05 UTCEPSS rescore
  20. 2026-06-23 21:33 UTCEPSS rescore
  21. 2026-06-22 14:25 UTCEPSS rescore
  22. 2026-06-22 14:25 UTCEPSS rescore
  23. 2026-06-21 14:56 UTCEPSS rescore
  24. 2026-06-21 14:56 UTCEPSS rescore
  25. 2026-06-21 01:59 UTCEPSS rescore
Show 52 more
  1. 2026-06-19 19:25 UTCEPSS rescore
  2. 2026-06-19 19:25 UTCEPSS rescore
  3. 2026-06-18 17:52 UTCEPSS rescore
  4. 2026-06-18 17:52 UTCEPSS rescore
  5. 2026-06-17 17:53 UTCEPSS rescore
  6. 2026-06-16 17:52 UTCEPSS rescore
  7. 2026-06-15 17:49 UTCEPSS rescore
  8. 2026-06-14 23:18 UTCEPSS rescore
  9. 2026-06-13 23:00 UTCEPSS rescore
  10. 2026-06-12 23:12 UTCEPSS rescore
  11. 2026-06-12 23:12 UTCEPSS rescore
  12. 2026-06-11 14:00 UTCEPSS rescore
  13. 2026-06-10 22:18 UTCEPSS rescore
  14. 2026-06-10 19:18 UTCNVD updateCVSS v3 → 5.3 · severity → MEDIUM
  15. 2026-06-10 14:28 UTCEG score recompute
  16. 2026-06-10 14:28 UTCGHSA enrichment
  17. 2026-06-10 13:22 UTCEPSS rescore
  18. 2026-06-08 14:17 UTCEPSS rescore
  19. 2026-06-08 14:17 UTCEPSS rescore
  20. 2026-06-07 10:34 UTCEG score recompute
  21. 2026-06-07 10:34 UTCGHSA enrichment
  22. 2026-06-05 22:47 UTCEPSS rescore
  23. 2026-06-05 22:47 UTCEPSS rescore
  24. 2026-06-05 06:10 UTCEPSS rescore
  25. 2026-06-05 06:10 UTCEPSS rescore
  26. 2026-06-04 13:12 UTCEPSS rescore
  27. 2026-06-04 13:12 UTCEPSS rescore
  28. 2026-06-01 13:52 UTCEPSS rescore
  29. 2026-06-01 13:52 UTCEPSS rescore
  30. 2026-06-01 13:51 UTCEPSS rescore
  31. 2026-05-31 22:30 UTCEPSS rescore
  32. 2026-05-31 22:30 UTCEPSS rescore
  33. 2026-05-31 00:16 UTCEPSS rescore
  34. 2026-05-31 00:16 UTCEPSS rescore
  35. 2026-05-31 00:16 UTCEPSS rescore
  36. 2026-05-29 13:44 UTCEPSS rescore
  37. 2026-05-29 13:44 UTCEPSS rescore
  38. 2026-05-28 13:44 UTCEPSS rescore
  39. 2026-05-28 13:44 UTCEPSS rescore
  40. 2026-05-28 13:44 UTCEPSS rescore
  41. 2026-05-27 13:40 UTCEPSS rescore
  42. 2026-05-27 13:40 UTCEPSS rescore
  43. 2026-05-27 13:40 UTCEPSS rescore
  44. 2026-05-26 13:44 UTCEPSS rescore
  45. 2026-05-26 07:18 UTCEPSS rescore
  46. 2026-05-26 07:18 UTCEPSS rescore
  47. 2026-05-20 22:38 UTCEPSS rescore
  48. 2026-05-20 22:38 UTCEPSS rescore
  49. 2026-05-20 18:58 UTCEG score recompute
  50. 2026-05-20 18:58 UTCGHSA enrichment
  51. 2026-05-20 11:22 UTCEPSS rescore
  52. 2026-05-20 11:22 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 16.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-37977?
CVE-2026-37977 has a CVSS v3 base score of 5.3 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 3.7.
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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-37977

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