An invalid read of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in mongoose.c in Cesanta…

published 2019-06-10 7y ago modified 2026-06-17 4mo ago also EUVD-2018-12914

cvss: 9.8; version 3.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 3.6%; EPSS 3.6% chance of exploitation in 30 days, percentile 89%
public exploits: 0; none known

An invalid read of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in mongoose.c in Cesanta Mongoose Embedded Web Server Library 6.13 and earlier allows a denial of service (application crash) or remote code execution.

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Exploit prediction

3.57% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

github.com https://github.com/insi2304/mongoose-6.13-fuzz/blob/master/Simplest_Web_Server_Use_After_Free-read_mg_http_free_proto_data_cgi.png referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.0	9.8	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	7.5	AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

CWE-416 Use After Free

References

github.com /insi2304/mongoose-6.13-fuzz/blob/master/Simplest_Web_Server_Use_After_Free-read_mg_http_free_proto_data_cgi.p
exploit, third-party-advisory

Sources

CVE List CVE-2018-20356
NVD CVE-2018-20356

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