Home/CVE/Non-constant-time comparison of CSRF tokens in endpoint request handler in com.vaadin:flow-server versions 3.0.0 through
CVE

CVE-2021-31406

Non-constant-time comparison of CSRF tokens in endpoint request handler in com.vaadin:flow-server versions 3.0.0 through

Non-constant-time comparison of CSRF tokens in endpoint request handler in com.vaadin:flow-server versions 3.0.0 through 5.0.3 (Vaadin 15.0.0 through 18.0.6), and com.vaadin:fusion-endpoint version 6.0.0 (Vaadin 19.0.0) allows attacker to guess a security token for Fusion endpoints via timing attack.

MEDIUM · CVSS 4 EPSS 0.00054
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules3 YARA rules0
⬡

Weakness Classification

CWE-203Observable Discrepancy
CWE-208Observable Timing Discrepancy
▤

Affected Products & Versions

4
vaadin flow>= 3.0.0 and < 5.0.4
vaadin flowall versions
vaadin>= 15.0.0 and < 18.0.7
vaadinall versions
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
Maven com.vaadin:flow-server MODERATE fixed in 5.0.4
◈

Sigma Hunt Rules

3
Exact rules name this CVE ID. Product rules name an affected product in their title. Related rules cover techniques used by actors who exploited this CVE. Showing the most relevant matches; the complete related set is on the full drill-down.
producthighAWS VPC Flow Logs Deleted
productmediumApplication Using Device Code Authentication Flow
productmediumApplications That Are Using ROPC Authentication Flow
▣

Scoring & Timeline

4
MEDIUM · CVSS v3.1 · security@vaadin.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD23 Apr 2021 · 04:15 PM
CVSS VectorCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/vaadin/flow/pull/10157PatchThird Party Advisory
https://vaadin.com/security/cve-2021-31406Vendor Advisory
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