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Fencer Vulns
medium 4.0

CVE-2021-31404 json

Timing side channel vulnerability in UIDL request handler in Vaadin 10, 11-14, and 15-18

published 2021-04-19 5 y ago modified 2026-06-17 4 mo ago also GHSA-xwg3-qrcg-w9x6 , EUVD-2021-0890

cvss
4.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

Non-constant-time comparison of CSRF tokens in UIDL request handler in com.vaadin:flow-server versions 1.0.0 through 1.0.13 (Vaadin 10.0.0 through 10.0.16), 1.1.0 prior to 2.0.0 (Vaadin 11 prior to 14), 2.0.0 through 2.4.6 (Vaadin 14.0.0 through 14.4.6), 3.0.0 prior to 5.0.0 (Vaadin 15 prior to 18), and 5.0.0 through 5.0.2 (Vaadin 18.0.0 through 18.0.5) allows attacker to guess a security token via timing attack.

Patch / fix

  • maven com.vaadin:flow-server 1.0.14, 2.4.7, 5.0.3
  • Vaadin Vaadin 14.0.0, 18.0.0
  • Vaadin flow-server 2.0.0, 5.0.0

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.0 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
NVD 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:P/I:N/A:N
GitHub 3.1 4.0 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
maven com.vaadin:flow-server
>=1.0.0, <1.0.14
>=1.1.0, <2.4.7
>=3.0.0, <5.0.3
1.0.14
2.4.7
5.0.3

Affected products

  • Vaadin Vaadin
  • Vaadin flow-server

Classification

Weakness
  • CWE-208 Observable Timing Discrepancy
  • CWE-203 Observable Discrepancy

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.