CVE-2026-73251

CRITICALPre-NVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 91% 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
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.3Exploit: None knownExposed: 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 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle. In src/tls_builtin.c, the mg_tls_init() function stores the bundle in tls->ca_bundle_der while tls->ca_der.len remains zero, and mg_tls_recv_cert() uses tls_bundle_find() to accept a Common Name match without calling mg_tls_verify_cert_signature(). A forged self-signed certificate can therefore satisfy hostname and CertificateVerify checks and enable interception, credential disclosure, traffic modification, and malicious responses. This issue is fixed in version 7.23.

CVSS v3
9.3
EG Score
9.3(medium)
EG Risk
46(Track)
EG Risk 46/100SSVC: 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
Severity93% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
9%
KEV
Not listed

Published

August 20, 2026

Last Modified

August 20, 2026

Advisory Details (3)

Auto-updated Aug 23, 2026
Patch available. Sources: github, github_commit, github_release.
github Patch Available

Built-in TLS: CA-bundle certificate chain accepted without any signature verification · Advisory · cesanta/mongoose · GitHub

https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
github_release Patch Available

Mongoose 7.23

Patch available: cesanta/mongoose 7.23

https://github.com/cesanta/mongoose/releases/tag/7.23
github_commit Patch Available

commit 2988bc9df3a5 (cesanta/mongoose)

Patch available: cesanta/mongoose 7.23 (contains commit 2988bc9df3a5)

https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 19× 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 03:45 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 15:50 UTCEG score recompute
  6. 2026-08-27 14:25 UTCEPSS rescore
  7. 2026-08-26 17:53 UTCEG score recompute
  8. 2026-08-26 14:47 UTCEPSS rescore
  9. 2026-08-25 15:01 UTCEG score recompute
  10. 2026-08-25 13:49 UTCEPSS rescore
  11. 2026-08-24 16:57 UTCEG score recompute
  12. 2026-08-24 11:56 UTCEG score recompute
  13. 2026-08-23 00:54 UTCEG score recompute
  14. 2026-08-23 00:19 UTCEPSS rescore
  15. 2026-08-22 03:00 UTCEG score recompute
  16. 2026-08-21 23:49 UTCEPSS rescore
  17. 2026-08-20 18:17 UTCEG score recompute
  18. 2026-08-20 17:46 UTCEG score recompute
  19. 2026-08-20 17:46 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-73251?
CVE-2026-73251 is a critical vulnerability published on August 20, 2026. Mongoose is an embedded web server and network library. Prior to 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle. In src/tlsbuiltin.c, the mgtlsinit() function stores the bundle in tls->cabundleder while tls->cader.len remains…
When was CVE-2026-73251 disclosed?
CVE-2026-73251 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-2026-73251 actively exploited?
CVE-2026-73251 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 90.7% of all scored CVEs.
What is the CVSS score of CVE-2026-73251?
CVE-2026-73251 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-73251?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-73251, 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.

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