CVE-2026-40170

Exploitation

Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.

SSVC decision

• ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
• AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.78% probability of exploitation activity in the next 30 days.

EPSS percentile

Ranks above 53.2% of scored records. A rank, not a probability.

NVD base score

7.5 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD analysis status

Modified. NVD last modified this record on 2026-07-15.

Red Hat severity

Important. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-04-16 21:34Z4 MO AGO

Last updated

2026-07-15 01:01Z1 MO AGO

Reserved

2026-04-09

Assigning CNA

GitHub_M

Record state

PUBLISHED

Severity

High (CVSS 7.5)

CNA CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weaknesses

• CWE-121Stack-based Buffer OverflowVariant
• CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')Base

Data version

5.2

Document digest

85c07149b48d7d81a9b39397d4eee8b76179cde13fbc4ffb2687508754872b01

• github.comhttps://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8fx_refsource_CONFIRM
• github.comhttps://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5x_refsource_MISC
• www.openwall.comhttp://www.openwall.com/lists/oss-security/2026/04/17/12
• access.redhat.comhttps://access.redhat.com/security/cve/CVE-2026-40170vdb-entryx_refsource_REDHAT
• bugzilla.redhat.comRHBZ#2459061https://bugzilla.redhat.com/show_bug.cgi?id=2459061issue-trackingx_refsource_REDHAT
• security.access.redhat.comhttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40170.jsonx_sadp-csaf-vex
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:22963vendor-advisoryx_refsource_REDHAT
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:25049vendor-advisoryx_refsource_REDHAT
• access.redhat.comhttps://access.redhat.com/errata/RHSA-2026:9113vendor-advisoryx_refsource_REDHAT