CVE-2026-5921

HIGHNVD 8.98.9—
EchelonGraph scoreMEDIUM confidence

Score 8.9 from GitHub Security Advisory (severity: HIGH) published 2026-04-22. NVD baseline CVSS 8.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
8.9EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.9Exploit: None knownExposed: 0

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

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the notebook viewer followed HTTP redirects without revalidating the destination host, enabling an unauthenticated SSRF to internal services. By chaining this with regex filter queries against an internal API and measuring response time differences, an attacker could infer secret values character by character. Exploitation required that private mode be disabled and that the attacker be able to chain the instance's open redirect endpoint through an external redirect to reach internal services. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5, and 3.20.1. This vulnerability was reported via the GitHub Bug Bounty program.

CVSS v3
8.9
EG Score
8.9(medium)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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
Severity89% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
35%
KEV
Not listed

Published

April 21, 2026

Last Modified

April 28, 2026

Advisory Details (7)

Auto-updated May 2, 2026
No patch confirmed yet.
generic

Release notes - GitHub Enterprise Server 3.20 Docs

https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1
generic

Release notes - GitHub Enterprise Server 3.19 Docs

https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5
generic

Release notes - GitHub Enterprise Server 3.18 Docs

https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8
generic

Release notes - GitHub Enterprise Server 3.17 Docs

https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.14
generic

Release notes - GitHub Enterprise Server 3.16 Docs

https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.17
generic

Release notes - GitHub Enterprise Server 3.15 Docs

https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.21
generic

Release notes - GitHub Enterprise Server 3.14 Docs

https://docs.github.com/en/enterprise-server@3.14/admin/release-notes#3.14.26

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 44× 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 118 total refreshes for this CVE.

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-5921?
CVE-2026-5921 is a high vulnerability published on April 21, 2026. A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the…
When was CVE-2026-5921 disclosed?
CVE-2026-5921 was first published in the National Vulnerability Database on April 21, 2026, with the most recent update on April 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-5921 actively exploited?
CVE-2026-5921 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 65.2% of all scored CVEs.
What is the CVSS score of CVE-2026-5921?
CVE-2026-5921 has a CVSS v3 base score of 8.9 (NVD).
How do I remediate CVE-2026-5921?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-5921, 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.

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