CVE-2026-59099

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-07-02. a secondary CVSS source baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this weekElevated
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.1Exploit: Elevated riskExposed: 0

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

Apereo CAS 7.3.0 before 8.0.0-RC6 contains a cryptographic vulnerability that allows remote unauthenticated attackers to recover plaintext conversation state by exploiting AES-GCM initialization vector reuse across the server lifetime. Attackers can collect multiple client-side webflow execution tokens from the unauthenticated login page and perform known-plaintext analysis to decrypt the webflow conversation state due to keystream reuse caused by a fixed all-zero IV paired with the same encryption key.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
72(Attend)
EG Risk 72/100SSVC: Attend

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
Severity91% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

July 2, 2026

Last Modified

July 14, 2026

Advisory Details (5)

Auto-updated Aug 1, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release.
generic

Apereo CAS 7.3.0 < 8.0.0-RC6 - AES-GCM Nonce Reuse Information Disclosure | Advisories | VulnCheck

https://www.vulncheck.com/advisories/apereo-cas-rc6-aes-gcm-nonce-reuse-information-disclosure
generic🟡 PoC Available

oss/cas.md at main · geo-chen/oss · GitHub

https://github.com/geo-chen/oss/blob/main/cas.md
github_release Patch Available

v8.0.0-RC6

Patch available: apereo/cas v8.0.0-RC6 (pre-release)

https://github.com/apereo/cas/releases/tag/v8.0.0-RC6
github_commit Patch Available

commit 22c6f4adf738 (apereo/cas)

Patch available: apereo/cas v8.0.0-RC6 (contains commit 22c6f4adf738)

https://github.com/apereo/cas/commit/22c6f4adf738852782309b523b4e80371057f2d0
generic🟡 PoC Available

CAS Vulnerability Disclosure – Apereo Community Blog

https://apereo.github.io/2026/06/18/vuln/

Vendor Advisories for CVE-2026-59099(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 44× in last 7d / 221× 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 355 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-59099?
CVE-2026-59099 is a critical vulnerability published on July 2, 2026. Apereo CAS 7.3.0 before 8.0.0-RC6 contains a cryptographic vulnerability that allows remote unauthenticated attackers to recover plaintext conversation state by exploiting AES-GCM initialization vector reuse across the server lifetime. Attackers can collect multiple client-side webflow execution…
When was CVE-2026-59099 disclosed?
CVE-2026-59099 was first published in the National Vulnerability Database on July 2, 2026, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-59099 actively exploited?
CVE-2026-59099 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 56.5% of all scored CVEs.
What is the CVSS score of CVE-2026-59099?
CVE-2026-59099 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-59099?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-59099, 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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