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TI-2026-85858 Aliases CVE-2026-123317GHSA-76h9-4mx5-8c9v

Session forgery in JetBrains Ktor via tampered encrypted session cookies

Priority LOW 37CWE-354Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

JetBrains Ktor before 3.6.1 does not properly validate the integrity check value of encrypted session cookies (CWE-354). A remote attacker with low privileges can tamper with a session cookie and forge a session.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Description from the CNA

In JetBrains Ktor before 3.6.1 session forgery was possible via tampered encrypted session cookies

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00204 10th percentileScored 2026-11-08
Fix Fixed Ktor (JetBrains): 3.6.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
JetBrainsKtorbefore 3.6.13.6.1Patch availableCNA
  • Ktor VendorJetBrains Affected before 3.6.1 Fixed in 3.6.1 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:jetbrains:ktor:*:*:*:*:*:*:*:*——JetBrains
  • cpe:2.3:a:jetbrains:ktor:*:*:*:*:*:*:*:* Versions — — ·JetBrains

Remediation

Update JetBrains Ktor to version 3.6.1, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

  • Fix · CNA Ktor (JetBrains) Fixed in 3.6.1

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    JetBrains Ktor 3.6.1

    3 records Highest priority Priority LOW 3 LOW

    Other records, highest priority first

    • TI-2026-85859 HTTP request smuggling in JetBrains Ktor CIO enginePriority LOW 21
    • TI-2026-85860 Cookie injection in JetBrains Ktor client cookie storagePriority LOW 17
    Show all 3 records →

Timeline

  1. 2026-11-06 Threatist record created from CVE-2026-123317
  2. 2026-11-06 Alias added: GHSA-76h9-4mx5-8c9v
  3. 2026-11-07 CISA SSVC decision points changed
  4. 2026-11-07 Priority changed: MEDIUM → LOW
  5. 2026-11-07 CISA SSVC decision points changed

References

Other 1

  • TI-2026-45031 Deserialization of untrusted data in JetBrains TeamCity KEVCVSS 3.1CRITICAL 9.8
  • TI-2024-18053 In JetBrains TeamCity before 2023.11.4 authentication bypass allowing to perform admin actions was possible KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-22884 In JetBrains TeamCity before 2023.05.4 authentication bypass leading to RCE on TeamCity Server was possible KEVCVSS 3.1CRITICAL 9.8
  • TI-2024-18054 In JetBrains TeamCity before 2023.11.4 path traversal allowing to perform limited admin actions was possible KEVCVSS 3.1HIGH 7.3
  • TI-2024-15905 In JetBrains TeamCity before 2023.11.3 authentication bypass leading to RCE was possible CVSS 3.1CRITICAL 9.8
  • TI-2024-24589 Insufficiently protected credentials in JetBrains IntelliJ IDEA CVSS 3.1CRITICAL 9.3
See all 787 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences