CVE-2026-88647

CRITICALPre-NVD 9.19.1
EchelonGraph scoreHIGH confidence

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

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-10-08. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: CISA-ADP (Vulnrichment) CVSS v3.1, EPSS, GitHub Security Advisory
Trending — 5 sources updated this weekElevated
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: 0.2%CVSS: 9.1Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

A hostname verification bypass in GnuTLS v3.8.13 allows attackers to circumvent the Common Name fallback mechanism and eavesdrop on communications via a crafted certificate.

CVSS v3
9.1
EG Score
9.1CRITICALhigh confidence
EG Risk
72
EG Risk 72/100

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.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (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 yes (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
0.2%
EPSS %ILE
10th
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 yes (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)3 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (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

October 8, 2026

Last Modified

October 10, 2026

Advisory Details (2)

Auto-updated Oct 10, 2026
Patch available.
Web page

gist:f98ec3de1a871fdfc02b70b8b9ba7642 · GitHub

https://gist.github.com/lkloliver/f98ec3de1a871fdfc02b70b8b9ba7642
Web page

gnutls CN fallback with unsupported SAN type (#1802) · Issues · gnutls / GnuTLS · GitLab

https://gitlab.com/gnutls/gnutls/-/issues/1802

Vendor Advisories for CVE-2026-88647(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
gnutls283.7.9-2 ... 3.8.9-3 (45 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
gnutls283.8.10-1 ... 3.8.9-3+deb13u4 (16 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
gnutls283.8.10-1 ... 3.8.9-3 (12 versions)
  • every version on: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 37× in last 7d / 37× 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.

  1. 2026-10-14 01:25 UTCEG score recompute
  2. 2026-10-14 01:25 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  3. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  4. 2026-10-12 21:37 UTCEG score recompute
  5. 2026-10-12 21:37 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  6. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  7. 2026-10-12 14:49 UTCEG score recompute
  8. 2026-10-12 03:56 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  9. 2026-10-11 23:52 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  10. 2026-10-11 19:49 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  11. 2026-10-11 19:15 UTCEG score recompute
  12. 2026-10-11 16:32 UTCEG score recompute
  13. 2026-10-11 15:46 UTCEG score recompute
  14. 2026-10-11 15:46 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  15. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  16. 2026-10-11 13:48 UTCEG score recompute
  17. 2026-10-11 11:44 UTCEG score recompute
  18. 2026-10-11 11:44 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  19. 2026-10-11 07:42 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  20. 2026-10-11 03:39 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  21. 2026-10-10 23:37 UTCEG score recompute
  22. 2026-10-10 23:37 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  23. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  24. 2026-10-10 19:34 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  25. 2026-10-10 15:30 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
Show 12 more
  1. 2026-10-10 11:26 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  2. 2026-10-10 07:24 UTCEG score recompute
  3. 2026-10-10 07:23 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q · GitHub severity CRITICAL · GitHub CVSS 9.1
  4. 2026-10-10 03:21 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q
  5. 2026-10-10 03:00 UTCEG score recomputeFirst assessed: 9.1 CRITICAL
  6. 2026-10-10 03:00 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q
  7. 2026-10-10 03:00 UTCMITRE cvelistV5CVSS v3 → 9.1 · severity → CRITICAL
  8. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.1% · 1st percentile
  9. 2026-10-08 21:38 UTCGHSA enrichmentGHSA-2j2x-fffq-ff4q
  10. 2026-10-08 17:25 UTCNVD update
  11. 2026-10-08 16:51 UTCEG score recompute
  12. 2026-10-08 16:51 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-88647?
CVE-2026-88647 is a critical-severity vulnerability; its CVE record was published on October 8, 2026. A hostname verification bypass in GnuTLS v3.8.13 allows attackers to circumvent the Common Name fallback mechanism and eavesdrop on communications via a crafted certificate.
When was the CVE record for CVE-2026-88647 published?
The CVE record for CVE-2026-88647 was published on October 8, 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 October 10, 2026; the record at its source may have been updated since.
Is CVE-2026-88647 actively exploited?
CVE-2026-88647 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (10th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-88647?
CVE-2026-88647 has a CVSS v3.1 base score of 9.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-88647?
A fix for CVE-2026-88647 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-88647 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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