CVE-2021-31404 | Timing side channel vulnerability in UIDL request handler in Vaadin 10, 11-14, and 15-18

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.

Published: 2021-04-23 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-31404 is rated Low Risk (20.8/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.04%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-31404

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.05% 0.04% -0.01%
2 2025-11-18 0.04% 0.05% +0.01%
3 2023-03-07 — 0.04% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-31404

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.0 3.1 MEDIUM
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 1.4 2.5 [email protected]
2.5 3.1 LOW
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 1.0 1.4 [email protected]
1.9 2.0 LOW
AV:L/AC:M/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 3.4 2.9 [email protected]

Weakness enumeration for CVE-2021-31404

GitHub Security Advisory for CVE-2021-31404

GHSA-xwg3-qrcg-w9x6 · Severity: medium · Ecosystem: maven — Timing side channel vulnerability in UIDL request handler in Vaadin 10, 11-14, and 15-18

Affected software / configurations for CVE-2021-31404

Vendor Product Version Raw CPE
vaadin flow >= 1.0.0, < 1.0.14 cpe:2.3:a:vaadin:flow:*:*:*:*:*:*:*:*
vaadin flow >= 1.1.0, < 2.0.0 cpe:2.3:a:vaadin:flow:*:*:*:*:*:*:*:*
vaadin flow >= 2.0.0, < 2.4.7 cpe:2.3:a:vaadin:flow:*:*:*:*:*:*:*:*
vaadin flow >= 3.0.0, < 5.0.0 cpe:2.3:a:vaadin:flow:*:*:*:*:*:*:*:*
vaadin flow >= 5.0.0, < 5.0.3 cpe:2.3:a:vaadin:flow:*:*:*:*:*:*:*:*
vaadin vaadin >= 10.0.0, < 10.0.17 cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*
vaadin vaadin >= 11.0.0, < 14.0.0 cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*
vaadin vaadin >= 14.0.0, < 14.4.7 cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*
vaadin vaadin >= 15.0.0, < 17.0.0 cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*
vaadin vaadin >= 18.0.0, < 18.0.6 cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*

References for CVE-2021-31404

URL Tags
https://github.com/vaadin/flow/pull/9875 Patch Third Party Advisory
https://vaadin.com/security/cve-2021-31404 Vendor Advisory
cvelogic Threat Intelligence