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CVE-2021-43203

24
FAUCET Score

CVE-2021-43203 describes an improper nonce verification vulnerability in JetBrains Ktor versions prior to 1.6.4, affecting its OAuth2 authentication process. This high-severity vulnerability (CVSS 7.5) has a low attack complexity and can lead to integrity compromise, as an attacker could bypass authentication without user interaction. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.6.4CPE matchmatch criteria
cpe:2.3:a:jetbrains:ktor:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.84%
Probability of exploitation in next 30 days
EPSS Percentile
54.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0084 is in the 29th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

blog.jetbrains.com / blog/2021/11/08/jetbrains-security-bulletin-q3-2021
Vendor Advisory