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CVE-2018-20355

31
FAUCET Score

CVE-2018-20355 is a critical use-after-free vulnerability in Cesanta Mongoose Embedded Web Server Library versions 6.13 and earlier, specifically within the mg_http_free_proto_data_cgi function. This flaw allows an unauthenticated attacker to trigger an invalid write, leading to a denial of service or potentially remote code execution. With a CVSS score of 9.8, it is easily exploitable over the network with no user interaction. While highly severe, there is currently no public exploit code, Metasploit modules, or evidence of active exploitation, and it has received minimal community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
<= 6.13CPE matchmatch criteria
cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
3.57%
Probability of exploitation in next 30 days
EPSS Percentile
88.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0357 is in the 81st percentile among its peer group of 36,829 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / insi2304/mongoose-6.13-fuzz/blob/master/Simplest_Web_Server_Use_After_Free-mg_http_free_proto_data_cgi.png
ExploitThird Party Advisory