CVE-2026-73253

CRITICAL

9.1

CVSS v4

Description

Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. This issue is fixed in version 7.22.

CWE-295Improper Certificate Validation

How to fix

Remediation Available

mongooseDebian

Fixed in:7.22+ds-1CVE-2026-73253

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v4 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

Impact

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/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:X/V:X/RE:X/U:X

Exploit Intelligence

0.21%probability of exploitation in 30 days

11thpercentile

Low risk: more likely to be exploited than 11% of all known CVEs.

References

Other references4

Related Vulnerabilities

Other CWE-295 (Improper Certificate Validation) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2015-4000	Low	3.7	100%	-	Fix
CVE-2020-0601	High	8.1	89%	KEV	Fix
CVE-2009-3555	Critical	9.8	87%	-	Fix
CVE-2022-26923	High	8.8	84%	KEV	Fix
CVE-2023-27823	Critical	9.8	53%	-	-
CVE-2022-42979	High	8.8	24%	-	-

Common questions

How do I fix CVE-2026-73253?

Upgrade mongoose on debian unstable to 7.22+ds-1 or later.

Is CVE-2026-73253 being actively exploited?

Not that we know of. CVE-2026-73253 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.21% is the estimated probability that it will be exploited in the next 30 days. That is higher than 11% of all scored CVEs.

How severe is CVE-2026-73253?

CVE-2026-73253 has a CVSS v4 base score of 9.1, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-73253 affect?

Published advisories record a fix for mongoose (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2026-73253

Markdown

[![CVE-2026-73253](https://tridentstack.com/cve/badge/CVE-2026-73253.svg)](https://tridentstack.com/cve/CVE-2026-73253)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-73253"><img src="https://tridentstack.com/cve/badge/CVE-2026-73253.svg" alt="CVE-2026-73253"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it works Start freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-20.