CVE-2026-40170

Advisory lineage Upstream: 0 Downstream: 17
Analyzed
Published: 16 Apr 2026, 21:34
Last modified:15 Jul 2026, 01:01

Vulnerability Summary

Overall Risk (default)
medium
40/100
CVSS Score
7.5 HIGH
v3.1 (cve.org)
EPSS Score
0.78% LOW
1% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
2 found
Dark Web
Not detected

Timeline

16 Apr 2026, 21:34
Published
Vulnerability first disclosed
15 Jul 2026, 01:01
Last Modified
Vulnerability information updated

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.

CVSS Metrics

  • v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 0.78%• Percentile: 51%

Techniques & Countermeasures

  • CWE-121•Stack-based Buffer Overflow

    A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

  • CWE-120•Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

    The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

Affected Systems

  • nghttp2•ngtcp2

    < 1.22.1

  • ngtcp2•ngtcp2

    < 1.22.1

  • tatsuhiro-t•ngtcp2

    < 1.22.1

References (9)