ngtcp2 is a C implementation of the IETF QUIC protocol. In versions prior to 1.22.1, ngtcp2_qlog_parameters_set_transport_params() serializes peer transport parameters into a fixed 1024-byte stack buffer without bounds checking. When qlog is enabled, a remote peer can send sufficiently large transport parameters during the QUIC handshake to cause writes beyond the buffer boundary, resulting in a stack buffer overflow. This affects deployments that enable the qlog callback and process untrusted peer transport parameters. This issue has been fixed in version 1.22.1. If developers are unable to immediately upgrade, they can disable the qlog on client.
CVE-2026-40170
“—” beside the score: it is equal to the CVSS score beside it.
This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 1.0% (60th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
- CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 65EG Risk 65/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.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 or medium mission impact; Attend at high (mission-essential systems).Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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
- 1.0%
- EPSS %ILE
- 60th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
- EG Likelihood
- 1.0% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-17). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
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 partial (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; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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
April 16, 2026
Last Modified
July 15, 2026
Advisory Details (3)
Auto-updated Jun 11, 2026qlog_parameters_set_transport_params_stack_overflow · Advisory · ngtcp2/ngtcp2 · GitHub
https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8foss-security - ngtcp2: qlog_parameters_set_transport_params_stack_overflow [CVE-2026-40170]
http://www.openwall.com/lists/oss-security/2026/04/17/12commit 708a7640c1f4 (ngtcp2/ngtcp2)
Fix landed in ngtcp2/ngtcp2 commit 708a7640c1f4 — awaiting tagged release
https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5Vendor Advisories for CVE-2026-40170(4)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:25049Red Hat Product SecurityCritical
Red Hat Security Advisory: samba security update
- RHSA-2026:22963Red Hat Product SecurityCritical
Red Hat Security Advisory: samba security update
- CVE-2026-40170Microsoft Security Response Center (MSRC)High
ngtcp2 has a qlog transport parameter serialization stack buffer overflow
- RHSA-2026:9113Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Patch Availability(4)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| ubuntu | ngtcp2-server (0.12.1+dfsg-1+deb12u1build0.24.04.1) @ noble | 2026-10-17 | ubuntu |
| redhat | samba-0:4.23.5-10.el9_8 | 2026-06-10 | redhat |
| redhat | samba-0:4.23.5-109.el10_2 | 2026-06-03 | redhat |
| redhat | ngtcp2-main-1.22.1-1.hum1 | 2026-04-20 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(8 across 8 ecosystems)
Alpine:v3.20(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | — |
| — |
Alpine:v3.21(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | — |
| — |
Alpine:v3.22(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | — |
| — |
Alpine:v3.23(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | — |
| — |
Alpine:v3.24(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | — |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | 0.12.1+dfsg-1 |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | 1.11.0-1 |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ngtcp2 | 1.11.0-1 ... 1.22.1-1~bpo13+1 (9 versions) |
| — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Additional Vendor Advisories
(1)
Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.
Data Freshness Timeline
(refreshed 10× in last 7d / 32× 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 99 of 226 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. 1 repeat row among the latest 100 is merged into the row it repeats. The 127 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-18 03:43 UTCEG score recompute
- 2026-10-17 16:34 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-17 14:54 UTCEG score recompute
- 2026-10-17 14:54 UTCVendor advisory
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-14 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-12 16:09 UTCEG score recompute
- 2026-10-11 19:52 UTCEG score recompute
- 2026-10-11 17:05 UTCEG score recompute
- 2026-10-11 14:31 UTCEG score recompute
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-10 19:33 UTCOSV refresh
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-08 17:12 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-06 15:17 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 1.0% · 60th percentile
- 2026-10-03 14:25 UTCEPSS rescoreEPSS 1.0% · 60th percentile
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- 2026-10-01 19:50 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-26 00:26 UTCEPSS rescoreEPSS 1.0% · 59th percentile
- 2026-09-21 06:49 UTCOSV refresh
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.8% · 54th percentile
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.8% · 54th percentile
- 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.8% · 54th percentile
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.8% · 54th percentile
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-02 04:58 UTCOSV refresh
- 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-16 06:34 UTCEG score recompute
- 2026-08-16 06:34 UTCVendor advisory
- 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-14 15:59 UTCVendor advisory
- 2026-08-14 04:39 UTCEG score recompute
- 2026-08-14 04:39 UTCVendor advisory
- 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-13 08:54 UTCVendor advisory
- 2026-08-12 18:50 UTCEG score recompute
- 2026-08-12 18:50 UTCVendor advisory
- 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-11 16:59 UTCEG score recompute
- 2026-08-11 16:59 UTCVendor advisory
- 2026-08-11 13:43 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-11 02:35 UTCEG score recompute
- 2026-08-11 02:35 UTCVendor advisory
- 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-10 02:36 UTCVendor advisory
- 2026-08-09 15:16 UTCEG score recompute
- 2026-08-09 15:16 UTCVendor advisory
- 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-09 03:56 UTCEG score recompute
- 2026-08-09 03:56 UTCVendor advisory
- 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-08 00:41 UTCEG score recompute
- 2026-08-08 00:41 UTCVendor advisory
- 2026-08-07 13:22 UTCEG score recompute
- 2026-08-07 13:22 UTCVendor advisory
- 2026-08-06 13:46 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-06 12:02 UTCVendor advisory
- 2026-08-05 23:20 UTCEG score recompute
- 2026-08-05 23:20 UTCVendor advisory
- 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-04 15:10 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
- 2026-08-04 10:38 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
Related CVEs(same vendor + same CWE)
Same vendor
5 shownredhat:RHSA-2026:22963
Frequently asked(5)
What is CVE-2026-40170?
When was the CVE record for CVE-2026-40170 published?
Is CVE-2026-40170 actively exploited?
What is the CVSS score of CVE-2026-40170?
How do I remediate CVE-2026-40170?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-40170
Is Your Infrastructure Affected by CVE-2026-40170?
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