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CVE-2021-31406

13
FAUCET Score

CVE-2021-31406 describes a timing attack vulnerability in Vaadin Flow (versions 3.0.0-5.0.3) and Vaadin Fusion (version 6.0.0) that allows an attacker to guess CSRF tokens due to non-constant-time comparisons. This vulnerability has a low CVSS score of 2.5, indicating a local attack vector with high attack complexity and a low impact on confidentiality. There is no evidence of active exploitation, publicly available exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 3.0.0, < 5.0.4CPE matchmatch criteria
cpe:2.3:a:vaadin:flow:*:*:*:*:*:*:*:*
6.0.0CPE matchmatch criteria
cpe:2.3:a:vaadin:flow:6.0.0:-:*:*:*:*:*:*
>= 15.0.0, < 18.0.7CPE matchmatch criteria
cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*
19.0.0CPE matchmatch criteria
cpe:2.3:a:vaadin:vaadin:19.0.0:-:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.0MEDIUM

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

Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
1.4
Impact Score
2.5
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.21%
Probability of exploitation in next 30 days
EPSS Percentile
11.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0021 is in the 40th percentile among its peer group of 223 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.2 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

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
mavenpatch availablevia ghsa
Product: com.vaadin:flow-serverFixed in: 5.0.4
mavenpatch availablevia ghsa
Product: com.vaadin:flow-serverFixed in: 6.0.1

Vendor Advisories (1)

mavenGHSA-p7jq-v8jp-j424medium

Timing side channel vulnerability in endpoint request handler in Vaadin 15-19

Apr 19, 2021

References

github.com / vaadin/flow/pull/10157
PatchThird Party Advisory
vaadin.com / security/cve-2021-31406
Vendor Advisory