CVE-2026-40170

HIGHPre-NVD 7.57.5
EchelonGraph scoreMEDIUM confidence

“—” 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.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Trending — 3 sources updated this weekElevated
7.5EG
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: 1.0%CVSS: 7.5Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
65
EG 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, 2026
Patch available. Sources: github_commit, github.
GitHub advisoryMentions a patch (unverified)

qlog_parameters_set_transport_params_stack_overflow · Advisory · ngtcp2/ngtcp2 · GitHub

https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f
Web page

oss-security - ngtcp2: qlog_parameters_set_transport_params_stack_overflow [CVE-2026-40170]

http://www.openwall.com/lists/oss-security/2026/04/17/12
GitHub commit

commit 708a7640c1f4 (ngtcp2/ngtcp2)

Fix landed in ngtcp2/ngtcp2 commit 708a7640c1f4 — awaiting tagged release

https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5

Patch Availability(4)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntungtcp2-server (0.12.1+dfsg-1+deb12u1build0.24.04.1) @ noble2026-10-17ubuntu
redhatsamba-0:4.23.5-10.el9_82026-06-10redhat
redhatsamba-0:4.23.5-109.el10_22026-06-03redhat
redhatngtcp2-main-1.22.1-1.hum12026-04-20redhat

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)
PackageVulnerable rangeFix by version rangeDependents
ngtcp2—
  • every version up to 1.5.0-r1: fixed in 1.5.0-r1
—
Alpine:v3.21(1)
PackageVulnerable rangeFix by version rangeDependents
ngtcp2—
  • every version up to 1.9.1-r1: fixed in 1.9.1-r1
—
Alpine:v3.22(1)
PackageVulnerable rangeFix by version rangeDependents
ngtcp2—
  • every version up to 1.12.0-r1: fixed in 1.12.0-r1
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
ngtcp2—
  • every version up to 1.22.1-r0: fixed in 1.22.1-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
ngtcp2—
  • every version up to 1.22.1-r0: fixed in 1.22.1-r0
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
ngtcp20.12.1+dfsg-1
  • every version up to 0.12.1+dfsg-1+deb12u1: fixed in 0.12.1+dfsg-1+deb12u1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
ngtcp21.11.0-1
  • every version up to 1.11.0-1+deb13u1: fixed in 1.11.0-1+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
ngtcp21.11.0-1 ... 1.22.1-1~bpo13+1 (9 versions)
  • every version up to 1.22.1-1: fixed in 1.22.1-1
—

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.

  1. 2026-10-19 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  2. 2026-10-18 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  3. 2026-10-18 03:43 UTCEG score recompute
  4. 2026-10-17 16:34 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  5. 2026-10-17 14:54 UTCEG score recompute
  6. 2026-10-17 14:54 UTCVendor advisory
  7. 2026-10-16 16:42 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  8. 2026-10-15 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  9. 2026-10-14 16:32 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  10. 2026-10-13 16:34 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  11. 2026-10-12 16:34 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  12. 2026-10-12 16:09 UTCEG score recompute
  13. 2026-10-11 19:52 UTCEG score recompute
  14. 2026-10-11 17:05 UTCEG score recompute
  15. 2026-10-11 14:31 UTCEG score recompute
  16. 2026-10-11 13:48 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  17. 2026-10-10 20:00 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  18. 2026-10-10 19:33 UTCOSV refresh
  19. 2026-10-09 20:07 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  20. 2026-10-08 17:12 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  21. 2026-10-07 23:48 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  22. 2026-10-06 15:17 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  23. 2026-10-05 17:43 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  24. 2026-10-04 23:22 UTCEPSS rescoreEPSS 1.0% · 60th percentile
  25. 2026-10-03 14:25 UTCEPSS rescoreEPSS 1.0% · 60th percentile
Show 74 more
  1. 2026-10-01 19:50 UTCEPSS rescoreEPSS 1.0% · 59th percentile
  2. 2026-09-30 15:03 UTCEPSS rescoreEPSS 1.0% · 59th percentile
  3. 2026-09-27 13:48 UTCEPSS rescoreEPSS 1.0% · 59th percentile
  4. 2026-09-26 15:58 UTCEPSS rescoreEPSS 1.0% · 59th percentile
  5. 2026-09-26 00:26 UTCEPSS rescoreEPSS 1.0% · 59th percentile
  6. 2026-09-21 06:49 UTCOSV refresh
  7. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  8. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  9. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  10. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  11. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  12. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  13. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  14. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  15. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  16. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  17. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  18. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  19. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  20. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  21. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  22. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  23. 2026-09-02 04:58 UTCOSV refresh
  24. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  25. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  26. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  27. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  28. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  29. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  30. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  31. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  32. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  33. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  34. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  35. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  36. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  37. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  38. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  39. 2026-08-16 06:34 UTCEG score recompute
  40. 2026-08-16 06:34 UTCVendor advisory
  41. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  42. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  43. 2026-08-14 15:59 UTCVendor advisory
  44. 2026-08-14 04:39 UTCEG score recompute
  45. 2026-08-14 04:39 UTCVendor advisory
  46. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  47. 2026-08-13 08:54 UTCVendor advisory
  48. 2026-08-12 18:50 UTCEG score recompute
  49. 2026-08-12 18:50 UTCVendor advisory
  50. 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  51. 2026-08-11 16:59 UTCEG score recompute
  52. 2026-08-11 16:59 UTCVendor advisory
  53. 2026-08-11 13:43 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  54. 2026-08-11 02:35 UTCEG score recompute
  55. 2026-08-11 02:35 UTCVendor advisory
  56. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  57. 2026-08-10 02:36 UTCVendor advisory
  58. 2026-08-09 15:16 UTCEG score recompute
  59. 2026-08-09 15:16 UTCVendor advisory
  60. 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  61. 2026-08-09 03:56 UTCEG score recompute
  62. 2026-08-09 03:56 UTCVendor advisory
  63. 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  64. 2026-08-08 00:41 UTCEG score recompute
  65. 2026-08-08 00:41 UTCVendor advisory
  66. 2026-08-07 13:22 UTCEG score recompute
  67. 2026-08-07 13:22 UTCVendor advisory
  68. 2026-08-06 13:46 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  69. 2026-08-06 12:02 UTCVendor advisory
  70. 2026-08-05 23:20 UTCEG score recompute
  71. 2026-08-05 23:20 UTCVendor advisory
  72. 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  73. 2026-08-04 15:10 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  74. 2026-08-04 10:38 UTCEPSS rescoreEPSS 0.8% · 52nd percentile

Frequently asked(5)

What is CVE-2026-40170?
CVE-2026-40170 is a high-severity vulnerability; its CVE record was published on April 16, 2026. ngtcp2 is a C implementation of the IETF QUIC protocol. In versions prior to 1.22.1, ngtcp2qlogparameterssettransport_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…
When was the CVE record for CVE-2026-40170 published?
The CVE record for CVE-2026-40170 was published on April 16, 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 July 15, 2026; the record at its source may have been updated since.
Is CVE-2026-40170 actively exploited?
CVE-2026-40170 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.0% probability of exploitation in the next 30 days (60th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-40170?
CVE-2026-40170 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-40170?
A fix for CVE-2026-40170 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-40170 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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