Buffer overflow in Apple Swift-Nio-Ssh

CVE-2026-43798

A single crafted SSH message gives an unauthenticated network attacker an out-of-bounds stack write of attacker-controlled length and content against any application built on swift-nio-ssh. This vulnerability is addressed in swift-nio-ssh version 0.14.1.

Vulnerability class: Buffer Overflow

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (38.5th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 38.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-43798: held from 0.003 to 0.005.

EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-43798?
CVE-2026-43798 is a critical-severity vulnerability in Apple Swift-Nio-Ssh, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2026-08-20.
How severe is CVE-2026-43798?
Critical severity. CVSS v3 base score is 9.8 out of 10.