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[USN-8300-1] ngtcp2 vulnerability

Posted on 25 May 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8300-1
May 25, 2026

ngtcp2 vulnerability
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 25.10
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

ngtcp2 could be made to run programs as your login if it received specially
crafted network traffic when qlog was enabled.

Software Description:
- ngtcp2: RFC9000 QUIC protocol implementation

Details:

Zou Dikai discovered that ngtcp2 serialized peer transport parameters into
a fixed 1024-byte stack buffer without bounds checking. When qlog was
enabled, a remote attacker could possibly use this issue to execute
arbitrary code.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
libngtcp2-16 1.16.0-1ubuntu0.1
libngtcp2-crypto-gnutls-dev 1.16.0-1ubuntu0.1
libngtcp2-crypto-gnutls8 1.16.0-1ubuntu0.1
libngtcp2-crypto-ossl-dev 1.16.0-1ubuntu0.1
libngtcp2-crypto-ossl0 1.16.0-1ubuntu0.1
libngtcp2-dev 1.16.0-1ubuntu0.1

Ubuntu 25.10
libngtcp2-16 1.11.0-1+deb13u1build0.25.10.1
libngtcp2-crypto-gnutls-dev 1.11.0-1+deb13u1build0.25.10.1
libngtcp2-crypto-gnutls8 1.11.0-1+deb13u1build0.25.10.1
libngtcp2-dev 1.11.0-1+deb13u1build0.25.10.1
ngtcp2-client 1.11.0-1+deb13u1build0.25.10.1
ngtcp2-server 1.11.0-1+deb13u1build0.25.10.1

Ubuntu 24.04 LTS
libngtcp2-9 0.12.1+dfsg-1+deb12u1build0.24.04.1
libngtcp2-crypto-gnutls-dev 0.12.1+dfsg-1+deb12u1build0.24.04.1
libngtcp2-crypto-gnutls2 0.12.1+dfsg-1+deb12u1build0.24.04.1
libngtcp2-dev 0.12.1+dfsg-1+deb12u1build0.24.04.1
ngtcp2-client 0.12.1+dfsg-1+deb12u1build0.24.04.1
ngtcp2-server 0.12.1+dfsg-1+deb12u1build0.24.04.1

Ubuntu 22.04 LTS
libngtcp2-0 0.1.0+dfsg-1ubuntu0.1~esm1
Available with Ubuntu Pro
libngtcp2-crypto-gnutls-dev 0.1.0+dfsg-1ubuntu0.1~esm1
Available with Ubuntu Pro
libngtcp2-crypto-gnutls0 0.1.0+dfsg-1ubuntu0.1~esm1
Available with Ubuntu Pro
libngtcp2-dev 0.1.0+dfsg-1ubuntu0.1~esm1
Available with Ubuntu Pro
ngtcp2-client 0.1.0+dfsg-1ubuntu0.1~esm1
Available with Ubuntu Pro
ngtcp2-server 0.1.0+dfsg-1ubuntu0.1~esm1
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8300-1
CVE-2026-40170

Package Information:
https://launchpad.net/ubuntu/+source/ngtcp2/1.16.0-1ubuntu0.1
https://launchpad.net/ubuntu/+source/ngtcp2/1.11.0-1+deb13u1build0.25.10.1
https://launchpad.net/ubuntu/+source/ngtcp2/0.12.1+dfsg-1+deb12u1build0.24.04.1

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