# CVE-2023-28321: Security feature bypass in https://github.com/curl/curl

> Attackers can bypass TLS certificate validation in curl by exploiting incorrect IDN wildcard matching, allowing man-in-the-middle attacks.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 May 2023
- **Updated:** 15 Jan 2025
- **Also known as:** ALPINE-CVE-2023-28321, AZL-26794, AZL-26808, AZL-26812, AZL-38032, CLEANSTART-2026-AH03908, CURL-CVE-2023-28321, DEBIAN-CVE-2023-28321, GHSA-pgq4-vq29-6v5r, JLSEC-2026-409, UBUNTU-CVE-2023-28321

## What is CVE-2023-28321?

CVE-2023-28321 is a medium-severity vulnerability in Apple Macos, published on 26 May 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An improper certificate validation vulnerability exists in curl <v8.1.0 in the way it supports matching of wildcard patterns when listed as "Subject Alternative Name" in TLS server certificates. curl can be built to use its own name matching function for TLS rather than one provided by a TLS library. This private wildcard matching function would match IDN (International Domain Name) hosts incorrectly and could as a result accept patterns that otherwise should mismatch. IDN hostnames are converted to puny code before used for certificate checks. Puny coded names always start with `xn--` and should not be allowed to pattern match, but the wildcard check in curl could still check for `x*`, which would match even though the IDN name most likely contained nothing even resembling an `x`.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2023-28321?

It affects 10 products.


Products: Apple Macos, Debian Debian Linux, Fedoraproject Fedora, Haxx Curl, Netapp Clustered Data Ontap, Netapp H300s Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H700s Firmware, Netapp Ontap Antivirus Connector.

## How do I fix CVE-2023-28321?

Upgrade to a fixed version.

## Is CVE-2023-28321 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-28321 exists.

## Other vulnerabilities in Apple Macos

- [CVE-2026-65400](https://insights.sbomify.com/CVE-2026-65400/): Apple macOS Improper Authentication (critical 9.8, exploited in the wild)
- [CVE-2024-44146](https://insights.sbomify.com/CVE-2024-44146/): Security feature bypass in macOS (critical 10.0)
- [CVE-2024-44148](https://insights.sbomify.com/CVE-2024-44148/): Security feature bypass in macOS (critical 10.0)
- [CVE-2023-38586](https://insights.sbomify.com/CVE-2023-38586/): Security feature bypass in macOS (critical 10.0)
- [CVE-2023-40455](https://insights.sbomify.com/CVE-2023-40455/): Security feature bypass in macOS (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-28321 and fix it if it is affected.

What it is: CVE-2023-28321 is a medium-severity vulnerability in Apple Macos, published on 26 May 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-28321 exists.

Affected product: Apple Macos. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-28321/ (Markdown: https://insights.sbomify.com/CVE-2023-28321/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-28321
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-28321
- OSV: https://osv.dev/vulnerability/CVE-2023-28321

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-28321/
Summaries are generated and may contain mistakes; the official description above is the record.