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Fencer Vulns
critical 9.8

CVE-2018-20354 json

An invalid read of 8 bytes due to a use-after-free vulnerability during a "return" in the mg_http_get_proto_data function in mongoose.c in…

published 2019-06-10 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-12912

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

Summary

An invalid read of 8 bytes due to a use-after-free vulnerability during a "return" in the mg_http_get_proto_data function 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.

Exploit prediction

3.57% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/insi2304/mongoose-6.13-fuzz/blob/master/Simplest_Web_Server_Use_After_Free-read-mg_http_get_proto_data.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

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.