CVE-2026-73253

CRITICALNVD 9.19.1
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This critical-severity CVE scores 9.1 under NVD CVSS v3. EPSS exploit probability: 0.3% (26th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Elevated
9.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 9.1Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
9.1CRITICALmedium confidence
EG Risk
57
EG Risk 57/100

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 (value × EchelonGraph’s weight)
Severity91% × 45%
The EG Score, 9.1 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
26th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 20, 2026

Last Modified

September 29, 2026

Advisory Details (4)

Auto-updated Sep 15, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
GitHub advisoryMentions a patch (unverified)

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 pull request 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

Affected Packages

(1 across 1 ecosystem)
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
mongoose7.21+ds-1, 7.21+ds-1~bpo13+1, 7.21+ds-2, 7.22+ds-1~bpo13+1
  • every version up to 7.22+ds-1: fixed in 7.22+ds-1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 53× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 98 of 99 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 2 repeat rows among the latest 100 are merged into the row they repeat. The 1 oldest row on record is not shown and was not checked, so the counts can still include repeats.

  1. 2026-10-14 01:44 UTCEG score recompute
  2. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  3. 2026-10-12 21:55 UTCEG score recompute
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 25th percentile
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  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 25th percentile
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  20. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 25th percentile
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  25. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 25th percentile
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  1. 2026-09-30 20:31 UTCEG score recompute
  2. 2026-09-29 15:46 UTCEG score recompute
  3. 2026-09-29 15:24 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  4. 2026-09-28 21:38 UTCEG score recompute
  5. 2026-09-28 16:00 UTCEG score recompute
  6. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  7. 2026-09-27 15:57 UTCEG score recompute
  8. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 26th percentile
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  10. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 26th percentile
  11. 2026-09-24 15:39 UTCEG score recompute
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  13. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  14. 2026-09-22 19:45 UTCEG score recompute
  15. 2026-09-21 21:48 UTCEG score recompute
  16. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  17. 2026-09-20 21:45 UTCEG score recompute
  18. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  19. 2026-09-19 18:29 UTCEG score recompute
  20. 2026-09-18 21:39 UTCEG score recompute
  21. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  22. 2026-09-17 21:19 UTCEG score recompute
  23. 2026-09-16 15:47 UTCEG score recompute
  24. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 11th percentile
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  26. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  27. 2026-09-15 03:43 UTCEG score recompute
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  29. 2026-09-13 20:14 UTCEG score recompute
  30. 2026-09-12 16:56 UTCEG score recompute
  31. 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  32. 2026-09-11 17:34 UTCEG score recompute
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  34. 2026-09-11 09:40 UTCEG score recompute
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  36. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  37. 2026-09-09 01:56 UTCEG score recompute
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  39. 2026-09-07 16:06 UTCEG score recompute
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  41. 2026-09-06 13:48 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  42. 2026-09-05 16:44 UTCEG score recompute
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  45. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.2% · 11th percentile
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  47. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  48. 2026-09-01 14:40 UTCEG score recompute
  49. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  50. 2026-09-01 06:51 UTCEG score recompute
  51. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  52. 2026-08-30 21:05 UTCEG score recompute
  53. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  54. 2026-08-30 01:30 UTCEG score recompute
  55. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  56. 2026-08-29 01:28 UTCEG score recompute
  57. 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  58. 2026-08-27 15:40 UTCEG score recompute
  59. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  60. 2026-08-26 16:14 UTCEG score recompute
  61. 2026-08-26 14:47 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  62. 2026-08-25 16:19 UTCEG score recompute
  63. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  64. 2026-08-24 16:57 UTCEG score recompute
  65. 2026-08-24 12:57 UTCEG score recompute
  66. 2026-08-23 01:52 UTCEG score recompute
  67. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  68. 2026-08-22 02:29 UTCEG score recompute
  69. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  70. 2026-08-20 19:18 UTCEG score recompute
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  72. 2026-08-20 18:17 UTCEG score recompute
  73. 2026-08-20 17:46 UTCEG score recomputeFirst assessed: 9.1 CRITICAL

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Frequently asked(5)

What is CVE-2026-73253?
CVE-2026-73253 is a critical-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-73253 published?
The CVE record for CVE-2026-73253 was published on August 20, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 29, 2026; the record at its source may have been updated since.
Is CVE-2026-73253 actively exploited?
CVE-2026-73253 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (26th percentile of EPSS-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?
A fix for CVE-2026-73253 is available: update to the fixed version the vendor names in its advisory.

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