CVE-2026-43820
SwiftNIO-SSL Out-of-Bounds Memory Access
Description
NIOSSLCertificate._subjectAlternativeNames provides access to the raw bytes for a cert's SANs. NIOSSL provides access to a buffer assumed to be backed by an ASN1_STRING, but not all SANs are backed by ASN1_STRING, so accessing the buffer for such a type can lead to out-of-bounds memory access. This vulnerability is addressed in swift-nio-ssl version 2.37.2.
INFO
Published Date :
July 23, 2026, 3:17 p.m.
Last Modified :
Sept. 4, 2026, 6:21 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
- Update swift-nio-ssl to version 2.37.2.
- Ensure SANs are validated before access.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-43820.
| URL | Resource |
|---|---|
| https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j | Vendor Advisory Exploit |
| https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j | Vendor Advisory Exploit |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-43820 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-43820
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-43820 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-43820 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Sep. 04, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:apple:swiftnio_ssl:*:*:*:*:*:*:*:* versions from (including) 2.18.0 up to (excluding) 2.37.2 Added Reference Type Apple Inc.: https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j Types: Exploit, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 24, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H Added CWE CWE-125 Added Reference https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j Added SSVC {'id': 'CVE-2026-43820', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-24T20:09:17.611102Z'} -
New CVE Received by [email protected]
Jul. 23, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Apple', 'product': 'swift-nio-ssl', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '2.37.2', 'versionType': 'custom'}]}] Added Description NIOSSLCertificate._subjectAlternativeNames provides access to the raw bytes for a cert's SANs. NIOSSL provides access to a buffer assumed to be backed by an ASN1_STRING, but not all SANs are backed by ASN1_STRING, so accessing the buffer for such a type can lead to out-of-bounds memory access. This vulnerability is addressed in swift-nio-ssl version 2.37.2. Added Reference https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j