CVE-2026-39324

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 80% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

Rack::Session is a session management implementation for Rack. From 2.0.0 to before 2.1.2, Rack::Session::Cookie incorrectly handles decryption failures when configured with secrets:. If cookie decryption fails, the implementation falls back to a default decoder instead of rejecting the cookie. This allows an unauthenticated attacker to supply a crafted session cookie that is accepted as valid session data without knowledge of any configured secret. Because this mechanism is used to load session state, an attacker can manipulate session contents and potentially gain unauthorized access. This vulnerability is fixed in 2.1.2.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
18.9%
KEV
Not listed

Published

April 7, 2026

Last Modified

April 15, 2026

Advisory Details (1)

Auto-updated Apr 29, 2026
Patch available. Sources: github.
github Patch Available

`Rack::Session::Cookie` decrypt failure falls back to accepting unencrypted cookies. · Advisory · rack/rack-session · GitHub

https://github.com/rack/rack-session/security/advisories/GHSA-33qg-7wpp-89cq

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubunturuby-rack-session (2.1.1-0.1ubuntu0.1) @ questing2026-06-12ubuntu
ubunturuby-rack-session (2.1.1-0.1ubuntu0.26.04.1) @ resolute2026-06-12ubuntu

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)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
rack-session2.0.0, 2.1.0, 2.1.12.1.2—

Weakness Classification(4)

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

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 34× 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 116 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-39324?
CVE-2026-39324 is a critical vulnerability published on April 7, 2026. Rack::Session is a session management implementation for Rack. From 2.0.0 to before 2.1.2, Rack::Session::Cookie incorrectly handles decryption failures when configured with secrets:. If cookie decryption fails, the implementation falls back to a default decoder instead of rejecting the cookie.…
When was CVE-2026-39324 disclosed?
CVE-2026-39324 was first published in the National Vulnerability Database on April 7, 2026, with the most recent update on April 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-39324 actively exploited?
CVE-2026-39324 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 18.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-39324?
CVE-2026-39324 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-39324?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-39324, 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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