Vulnerability · Published Apr 16, 2026 · Assigned by GitHub_M
CVE-2026-40170ngtcp2 has a qlog transport parameter serialization stack buffer overflow
High 7.5
In plain English
A high-severity stack buffer overflow in ngtcp2 from ngtcp2. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 56% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.8%top 44.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | ldb-tools | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | ldb-tools | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libldb | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libldb | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libldb-devel | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libldb-devel | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libnetapi | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libnetapi | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libnetapi-devel | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libnetapi-devel | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libsmbclient | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libsmbclient | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libsmbclient-devel | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libsmbclient-devel | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libwbclient | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libwbclient | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | libwbclient-devel | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | libwbclient-devel | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | python3-ldb | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | python3-ldb | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | python3-samba | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | python3-samba | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | python3-samba-dc | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | python3-samba-dc | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | python3-samba-test | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | python3-samba-test | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-client | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-client | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-client-libs | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-client-libs | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-common | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-common | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-common-libs | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-common-libs | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-common-tools | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-common-tools | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-dc-libs | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-dc-libs | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-dcerpc | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-dcerpc | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-devel | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-devel | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-gpupdate | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-gpupdate | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-krb5-printing | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-krb5-printing | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-ldb-ldap-modules | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-ldb-ldap-modules | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-libs | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-libs | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-pidl | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-pidl | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-test | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-test | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-test-libs | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-test-libs | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-tools | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-tools | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-usershares | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-usershares | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-vfs-iouring | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-vfs-iouring | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-winbind | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-winbind | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-winbind-clients | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-winbind-clients | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-winbind-krb5-locator | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-winbind-krb5-locator | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-winbind-modules | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-winbind-modules | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| AlmaLinux:10 | samba-winexe | 4.23.5-109.el10_2 | ALSA-2026:22963 |
| AlmaLinux:9 | samba-winexe | 4.23.5-10.el9_8 | ALSA-2026:25049 |
| Alpine:v3.20 | ngtcp2 | 1.5.0-r1 | ALPINE-CVE-2026-40170 |
| Alpine:v3.21 | ngtcp2 | 1.9.1-r1 | ALPINE-CVE-2026-40170 |
| Alpine:v3.22 | ngtcp2 | 1.12.0-r1 | ALPINE-CVE-2026-40170 |
| Alpine:v3.23 | ngtcp2 | 1.22.1-r0 | ALPINE-CVE-2026-40170 |
| Alpine:v3.24 | ngtcp2 | 1.22.1-r0 | ALPINE-CVE-2026-40170 |
| Debian:12 | ngtcp2 | 0.12.1+dfsg-1+deb12u1 | DEBIAN-CVE-2026-40170 |
| Debian:13 | ngtcp2 | 1.11.0-1+deb13u1 | DEBIAN-CVE-2026-40170 |
| Debian:14 | ngtcp2 | 1.22.1-1 | DEBIAN-CVE-2026-40170 |
| Rocky Linux:10 | samba | 0:4.23.5-109.el10_2 | RLSA-2026:22963 |
| Rocky Linux:9 | samba | 0:4.23.5-10.el9_8 | RLSA-2026:25049 |
| Ubuntu:24.04:LTS | ngtcp2 | 0.12.1+dfsg-1+deb12u1build0.24.04.1 | UBUNTU-CVE-2026-40170 |
| Ubuntu:25.10 | ngtcp2 | 1.11.0-1+deb13u1build0.25.10.1 | UBUNTU-CVE-2026-40170 |
| Ubuntu:26.04:LTS | ngtcp2 | 1.16.0-1ubuntu0.1 | UBUNTU-CVE-2026-40170 |
Affected products (as reported)
Weakness: CWE-121, CWE-120 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f x_refsource_CONFIRM
- https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5 x_refsource_MISC
- http://www.openwall.com/lists/oss-security/2026/04/17/12
- https://access.redhat.com/security/cve/CVE-2026-40170 vdb-entry, x_refsource_REDHAT
- RHBZ#2459061 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40170.json x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:22963 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:25049 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:9113 vendor-advisory, x_refsource_REDHAT