CVE-2021-3355

Exp

A stored-self XSS exists in LightCMS v1.3.4, allowing an attacker to execute HTML or JavaScript code in a vulnerable Title field to /admin/SensitiveWords.

Published: 2021-02-24 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3355 is rated High Exploit Risk (69.3/100): CVSS Medium severity, with high exploitation likelihood (EPSS 7.25%, 94th percentile). 5 public exploit reference(s) are indexed (Exploit-DB). 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-2021-3355

EDB-ID Source Kind Published Link
49598 exploit_db edb 2021-02-26 Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-3355

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 2026-06-28 7.28% 7.25% -0.03%
2 2026-06-15 0.21% 7.28% +7.07%
3 2025-11-21 — 0.21% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3355

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
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.
 2.3 2.7 [email protected]
3.5 2.0 LOW
AV:N/AC:M/Au:S/C:N/I:P/A:N 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:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 6.8 2.9 [email protected]

Weakness enumeration for CVE-2021-3355

Affected software / configurations for CVE-2021-3355

Vendor Product Version Raw CPE
lightcms_project lightcms 1.3.4 cpe:2.3:a:lightcms_project:lightcms:1.3.4:*:*:*:*:*:*:*

References for CVE-2021-3355

URL Tags
http://packetstormsecurity.com/files/161562/LightCMS-1.3.4-Cross-Site-Scripting.html Exploit Third Party Advisory VDB Entry
https://gist.github.com/Peithon/1c628ded0c4fc96c6331c3cce1d0c69b Exploit Third Party Advisory
https://github.com/eddy8/LightCMS/issues/18 Exploit Issue Tracking Third Party Advisory
https://www.exploit-db.com/exploits/49598 Exploit Third Party Advisory VDB Entry
cvelogic Threat Intelligence