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CVE-2021-21799

38
FAUCET Score

CVE-2021-21799 describes a cross-site scripting (XSS) vulnerability in the telnet_form.php script of Advantech R-SeeNet version 2.4.12. An unauthenticated attacker can exploit this by crafting a malicious URL, leading to arbitrary JavaScript execution in the victim's browser. With a CVSS score of 6.1 (Medium), this vulnerability requires user interaction (UI:R) and has low impact on confidentiality and integrity. While not listed in CISA's KEV catalog, exploit intelligence indicates the availability of Nuclei templates and significant community discussion, suggesting potential for exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
2.4.12CPE matchmatch criteria
cpe:2.3:a:advantech:r-seenet:2.4.12:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.6CRITICAL

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
6.0
CvssVersion
3.0

Exploit Intelligence

EPSS Score
12.29%
Probability of exploitation in next 30 days
EPSS Percentile
95.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-21799 · Aug 5, 2022
This CVE's current EPSS score of 0.1229 is in the 98th percentile among its peer group of 26,221 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

talosintelligence.com / vulnerability_reports/TALOS-2021-1270
ExploitThird Party Advisory