CVE-2026-73253

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 89% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
57(Track*)
EG Risk 57/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
11%
KEV
Not listed

Published

August 20, 2026

Last Modified

August 20, 2026

Advisory Details (4)

Auto-updated Aug 29, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github_release, github.
github Patch Available🟡 PoC Available

TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching · Advisory · cesanta/mongoose · GitHub

https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp
github_release Patch Available

Mongoose 7.22

Patch available: cesanta/mongoose 7.22

https://github.com/cesanta/mongoose/releases/tag/7.22
github_pr Patch Available

assorted patches

Patch available: cesanta/mongoose 7.22 (PR #3611 merged 2026-06-23)

https://github.com/cesanta/mongoose/pull/3611
github_commit Patch Available

commit a9df523f76f4 (cesanta/mongoose)

Patch available: cesanta/mongoose 7.22 (contains commit a9df523f76f4)

https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 21× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 01:30 UTCEG score recompute
  2. 2026-08-30 01:22 UTCEPSS rescore
  3. 2026-08-29 01:28 UTCEG score recompute
  4. 2026-08-28 21:42 UTCEPSS rescore
  5. 2026-08-27 15:40 UTCEG score recompute
  6. 2026-08-27 14:25 UTCEPSS rescore
  7. 2026-08-26 16:14 UTCEG score recompute
  8. 2026-08-26 14:47 UTCEPSS rescore
  9. 2026-08-25 16:19 UTCEG score recompute
  10. 2026-08-25 13:49 UTCEPSS rescore
  11. 2026-08-24 16:57 UTCEG score recompute
  12. 2026-08-24 12:57 UTCEG score recompute
  13. 2026-08-23 01:52 UTCEG score recompute
  14. 2026-08-23 00:19 UTCEPSS rescore
  15. 2026-08-22 02:29 UTCEG score recompute
  16. 2026-08-21 23:49 UTCEPSS rescore
  17. 2026-08-20 19:18 UTCEG score recompute
  18. 2026-08-20 18:52 UTCEG score recompute
  19. 2026-08-20 18:17 UTCEG score recompute
  20. 2026-08-20 17:46 UTCEG score recompute
  21. 2026-08-20 17:46 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-73253?
CVE-2026-73253 is a critical vulnerability published on August 20, 2026. 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 mgtlsverifycertsan() and mgtlsverifycertcn() functions in…
When was CVE-2026-73253 disclosed?
CVE-2026-73253 was first published in the National Vulnerability Database on August 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-73253 actively exploited?
CVE-2026-73253 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 88.6% of all scored CVEs.
What is the CVSS score of CVE-2026-73253?
CVE-2026-73253 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-73253?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-73253, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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