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Vulnerability record · CVE-2026-5246 · published 2 April 2026

CVE-2026-5246: Cesanta mongoose improper authorization vulnerability

Cesanta · Mongoose

A vulnerability was determined in Cesanta Mongoose up to 7.20. Affected is the function mg_tls_verify_cert_signature of the file mongoose.c of the component P-384 Public Key Handler. Executing a manipulation can lead to authorization bypass. The attack can be executed remotely. Attacks of this nature are highly complex. The exploitability is told to be difficult. The exploit has been publicly disclosed and may be utilized. Upgrading to version 7.21 is able to address this issue. This patch is called 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. The affected component should be upgraded. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

2.9 CVSS 4.0 Low EPSS 0.57% · top 54.5% CWE-285 · Improper authorizationCWE-639 · Insecure direct object reference
2.9CVSS 4.0 base score, v2 5.1
0.57%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

Description

A vulnerability was determined in Cesanta Mongoose up to 7.20. Affected is the function mg_tls_verify_cert_signature of the file mongoose.c of the component P-384 Public Key Handler. Executing a manipulation can lead to authorization bypass. The attack can be executed remotely. Attacks of this nature are highly complex. The exploitability is told to be difficult. The exploit has been publicly disclosed and may be utilized. Upgrading to version 7.21 is able to address this issue. This patch is called 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. The affected component should be upgraded. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/cesanta/mongoose/ Product
https://github.com/cesanta/mongoose/commit/0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1 Patch
https://github.com/cesanta/mongoose/releases/tag/7.21 ProductRelease Notes
https://vuldb.com/submit/770104 Third Party AdvisoryVDB Entry
https://vuldb.com/vuln/354827 Third Party AdvisoryVDB Entry
https://vuldb.com/vuln/354827/cti Permissions RequiredVDB Entry

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2024-42383Cesanta mongoose vulnerabilityUse of Out-of-range Pointer Offset vulnerability in Cesanta Mongoose Web Server v7.14 allows to write a NULL byte value beyond the memory space dedic…EPSS 0.27%9.8CVE-2020-25756Cesanta mongoose classic buffer overflow vulnerabilityA buffer overflow vulnerability exists in the mg_get_http_header function in Cesanta Mongoose 6.18 due to a lack of bounds checking. A crafted HTTP h…EPSS 1.6%9.8CVE-2019-19307Cesanta mongoose out-of-bounds read vulnerabilityAn integer overflow in parse_mqtt in mongoose.c in Cesanta Mongoose 6.16 allows an attacker to achieve remote DoS (infinite loop), or possibly cause …EPSS 42%9.8CVE-2019-12951Cesanta mongoose out-of-bounds write vulnerabilityAn issue was discovered in Mongoose before 6.15. The parse_mqtt() function in mg_mqtt.c has a critical heap-based buffer overflow.EPSS 2.0%9.8CVE-2018-20354Cesanta mongoose use after free vulnerabilityAn 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 Mo…EPSS 3.6%9.8CVE-2018-20355Cesanta mongoose use after free vulnerabilityAn invalid write 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 …EPSS 3.6%9.8CVE-2018-20353Cesanta mongoose use after free vulnerabilityAn invalid read of 8 bytes due to a use-after-free vulnerability during a "NULL test" in the mg_http_get_proto_data function in mongoose.c in Cesanta…EPSS 3.6%9.8CVE-2018-20356Cesanta mongoose use after free vulnerabilityAn 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 E…EPSS 3.6%

Source: NIST National Vulnerability Database (record CVE-2026-5246), CISA KEV, FIRST EPSS (scores of 2026-10-06). This page is refreshed as NVD updates the record.