CVE-2026-5246Public exploitNetwork attack vector

Unauthenticated mTLS bypass via skipped P-384 verification

Published Apr 2, 2026 · Updated Apr 2, 2026

Authentication bypass in Cesanta Mongoose 7.0 through 7.20 allows remote attackers to defeat mutual TLS via a client certificate. In mg_tls_verify_cert_signature, the 96-byte P-384 issuer-key branch returns success without checking the certificate signature. Exposure requires the built-in TLS stack and an mTLS server configured with a P-384 CA; any client certificate is then accepted regardless of issuer.

CVSS severity5.6
Medium
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Cesanta Mongoose 7.0 through 7.20 allows remote attackers to defeat mutual TLS via a client certificate. In mg_tls_verify_cert_signature, the 96-byte P-384 issuer-key branch returns success without checking the certificate signature. Exposure requires the built-in TLS stack and an mTLS server configured with a P-384 CA; any client certificate is then accepted regardless of issuer.

The record

CVE
CVE-2026-5246
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
Cesanta
Product
Mongoose
Classifications
CWE-285, CWE-639, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=7.0
  2. Affected versionversion=7.1
  3. Affected versionversion=7.10
  4. Affected versionversion=7.11
  5. Affected versionversion=7.12
  6. Affected versionversion=7.13
  7. Affected versionversion=7.14
  8. Affected versionversion=7.15
  9. Affected versionversion=7.16
  10. Affected versionversion=7.17
  11. Affected versionversion=7.18
  12. Affected versionversion=7.19
  13. Affected versionversion=7.2
  14. Affected versionversion=7.20
  15. Affected versionversion=7.3
  16. Affected versionversion=7.4
  17. Affected versionversion=7.5
  18. Affected versionversion=7.6
  19. Affected versionversion=7.7
  20. Affected versionversion=7.8
  21. Affected versionversion=7.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cesanta · Mongooseversion=7.0; version=7.1; version=7.10; version=7.11; version=7.12; version=7.13; version=7.14; version=7.15; version=7.16; version=7.17; version=7.18; version=7.19; version=7.2; version=7.20; version=7.3; version=7.4; version=7.5; version=7.6; version=7.7; version=7.8; version=7.9

Published CVSS scores

5.6VulDBCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
5.1VulDBAV:N/AC:H/Au:N/C:P/I:P/A:P
8.1NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
2.9VulDBCVSS: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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-285Improper Authorization
CWE-639Authorization Bypass Through User-Controlled Key
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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