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VulnerabilityPublished

CVE-2026-123317: JetBrains Ktor · Improper Validation of Integrity Check Value

Affects JetBrains KtorSource CVE Database V5

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Not known to be exploited · CVSS 8.1 High : upgrade to 3.6.1 soon.

Data as of 6 Nov 2026, 10:49 UTC

CVSS 3.1 base score
8.1High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (JetBrains)CVSS 3.18.1
Patch
Available – fixed in 3.6.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 6 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade JetBrains Ktor to 3.6.1.

Affected software

ProductAffectedFixed in
JetBrainsKtorAffected
  • <3.6.1
Fixed in
  • 3.6.1

AI-suggested

Upgrade JetBrains Ktor to version 3.6.1 or later, where this vulnerability is fixed. No additional mitigation is required once the update is applied.

Description

CVE-2026-123317 is a vulnerability in JetBrains Ktor versions before 3.6.1 that allows session forgery through tampered encrypted session cookies due to improper validation of integrity check values. This flaw enables attackers with low privileges to compromise session integrity without user interaction. The issue is fixed in version 3.6.1.

References

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