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TI-2026-28984 Aliases CVE-2026-40170

ngtcp2 has a qlog transport parameter serialization stack buffer overflow

Priority HIGH 72CWE-121Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-121 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00776 56th percentileScored 2026-11-07
Public exploit Yes 2 exploit referencesTagged by NVD
Fix Fixed ngtcp2 (ngtcp2): 1.22.1Red Hat: 3 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ngtcp2ngtcp2before 1.22.11.22.1Patch availableCNA
  • ngtcp2 Vendorngtcp2 Affected before 1.22.1 Fixed in 1.22.1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:tatsuhiro-t:ngtcp2:*:*:*:*:*:*:*:*before 1.22.1VulnerableTatsuhiro-t
  • cpe:2.3:a:tatsuhiro-t:ngtcp2:*:*:*:*:*:*:*:* Versions before 1.22.1 Vulnerable ·Tatsuhiro-t

Remediation

  • Fix · CNA ngtcp2 (ngtcp2) Fixed in 1.22.1

Red Hat 3 advisories

  • RHSA-2026:25049 Released 2026-06-10 · Red Hat rating Critical
    samba security update
    • Red Hat Enterprise Linux AppStream (v. 9) samba-client-4.23.5-10.el9_8, samba-gpupdate-4.23.5-10.el9_8, samba-krb5-printing-4.23.5-10.el9_8 +4
    • Red Hat Enterprise Linux BaseOS (v. 9) ldb-tools-4.23.5-10.el9_8, libldb-4.23.5-10.el9_8, libnetapi-4.23.5-10.el9_8 +18
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libldb-devel-4.23.5-10.el9_8, libnetapi-devel-4.23.5-10.el9_8, libsmbclient-devel-4.23.5-10.el9_8 +6
    • Red Hat Enterprise Linux Resilient Storage (v. 9) ctdb-4.23.5-10.el9_8
  • RHSA-2026:22963 Released 2026-06-03 · Red Hat rating Critical
    samba security update
    • Red Hat Enterprise Linux AppStream (v. 10) samba-client-4.23.5-109.el10_2, samba-gpupdate-4.23.5-109.el10_2, samba-krb5-printing-4.23.5-109.el10_2 +4
    • Red Hat Enterprise Linux BaseOS (v. 10) ldb-tools-4.23.5-109.el10_2, libldb-4.23.5-109.el10_2, libnetapi-4.23.5-109.el10_2 +18
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libldb-devel-4.23.5-109.el10_2, libnetapi-devel-4.23.5-109.el10_2, libsmbclient-devel-4.23.5-109.el10_2 +6
  • RHSA-2026:9113 Released 2026-04-20 · Red Hat rating Important
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images ngtcp2-1.22.1-1.hum1@aarch64, ngtcp2-1.22.1-1.hum1@src, ngtcp2-1.22.1-1.hum1@x86_64 +12

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:22963
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:25049
Red Hat Enterprise Linux BaseOS (v. 10)Fixed RHSA-2026:22963
Red Hat Enterprise Linux BaseOS (v. 9)Fixed RHSA-2026:25049
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:22963
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)Fixed RHSA-2026:25049
Red Hat Enterprise Linux Resilient Storage (v. 9)Fixed RHSA-2026:25049
Red Hat Hardened ImagesFixed RHSA-2026:9113
Not affected: 3 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-40170

References

Exploit 2

Patch 1

  • TI-2024-35323 Acks not validated before logged to qlog leads to buffer overflow in ngtcp2 CVSS 3.1HIGH 8.2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences