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» CVE-2021-3689
yii2 is vulnerable to Use of Predictable Algorithm in Random Number Generator
NVD Status： Modified ，CVE State: published
Threat Intelligence & Risk Assessment for CVE-2021-3689
Conclusion & alert: CVE-2021-3689 is rated High Exploit Risk (67/100) : CVSS High severity, with medium exploitation likelihood (EPSS 0.45%).Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB).Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
Public exploit references (Exploit-DB) for CVE-2021-3689
EDB-ID
Source
Kind
Published
Link
—
nvd_ref
exploit_tag
Exploit-DB ↗
Exploit prediction scoring system (EPSS) score for CVE-2021-3689
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
2025-12-23
0.51%
0.45%
-0.06%
2
2025-11-21
0.45%
0.51%
+0.06%
3
2025-11-18
—
0.45%
—
Full EPSS history
(13 records total)
Common vulnerability scoring system (CVSS) metrics for CVE-2021-3689
CVSS metrics for this CVE.
Base score
Version
Severity
Vector
Exploitability
Impact
Score source
7.5
3.1
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
3.9
3.6
[email protected]
8.1
3.0
HIGH
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
2.2
5.9
[email protected]
5.0
2.0
MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/A:N
Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
10.0
2.9
[email protected]
Weakness enumeration for CVE-2021-3689
GitHub Security Advisory for CVE-2021-3689
GHSA-hq3v-rg6f-6hx4 · Severity: high · Ecosystem: composer
— Use of Insufficiently Random Values in yiisoft/yii2-dev
Affected software / configurations for CVE-2021-3689
Vendor
Product
Version
Raw CPE
yiiframework
yii
>= 2.0.0, < 2.0.43
cpe:2.3:a:yiiframework:yii:*:*:*:*:*:*:*:*
References for CVE-2021-3689
cvelogic
Threat Intelligence