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» CVE-2021-21956
A php unserialize vulnerability exists in the Ai-Bolit functionality of CloudLinux Inc Imunify360 5.10.2. A specially-crafted malformed file can lead to potential arbitrary command execution. An attacker can provide a malicious file to trigger this vulnerability.
NVD Status： Modified ，CVE State: published
Threat Intelligence & Risk Assessment for CVE-2021-21956
Conclusion & alert: CVE-2021-21956 is rated High Exploit Risk (70.1/100) : CVSS High severity, with medium exploitation likelihood (EPSS 1.27%).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-2021-21956
EDB-ID
Source
Kind
Published
Link
—
nvd_ref
exploit_tag
Exploit-DB ↗
Exploit prediction scoring system (EPSS) score for CVE-2021-21956
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
2026-06-15
0.43%
1.27%
+0.83%
2
2025-11-21
0.33%
0.43%
+0.10%
3
2025-11-18
—
0.33%
—
Full EPSS history
(11 records total)
Common vulnerability scoring system (CVSS) metrics for CVE-2021-21956
CVSS metrics for this CVE.
Base score
Version
Severity
Vector
Exploitability
Impact
Score source
7.8
3.1
HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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: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:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
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.
1.8
5.9
[email protected]
8.2
3.0
HIGH
CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:C/C:H/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: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:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
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:N)
Service keeps running; no real outage angle.
1.8
5.8
[email protected]
9.3
2.0
HIGH
AV:N/AC:M/Au:N/C:C/I:C/A:C
Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
8.6
10.0
[email protected]
Weakness enumeration for CVE-2021-21956
Affected software / configurations for CVE-2021-21956
References for CVE-2021-21956
cvelogic
Threat Intelligence