# CVE-2023-27538: Auth bypass in https://github.com/curl/curl

> Attackers can bypass authentication by reusing SSH connections with mismatched settings in libcurl, potentially accessing unauthorized resources.

- **Severity:** High 7.7 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 30 Mar 2023
- **Updated:** 14 Oct 2026
- **Also known as:** ALPINE-CVE-2023-27538, AZL-25786, AZL-25803, AZL-25808, AZL-25848, AZL-34613, AZL-38257, CLEANSTART-2026-RQ73430, CURL-CVE-2023-27538, DEBIAN-CVE-2023-27538, GHSA-cgj3-cvg6-pcvh, JLSEC-2025-33, UBUNTU-CVE-2023-27538

## What is CVE-2023-27538?

CVE-2023-27538 is a high-severity authentication bypass vulnerability in Debian Debian Linux, published on 30 Mar 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An authentication bypass vulnerability exists in libcurl prior to v8.0.0 where it reuses a previously established SSH connection despite the fact that an SSH option was modified, which should have prevented reuse. libcurl maintains a pool of previously used connections to reuse them for subsequent transfers if the configurations match. However, two SSH settings were omitted from the configuration check, allowing them to match easily, potentially leading to the reuse of an inappropriate connection.

Weakness: CWE-287 (Improper Authentication), CWE-305 (Authentication Bypass by Primary Weakness)

## Which versions are affected by CVE-2023-27538?

It affects 11 products.


Products: Broadcom Brocade Fabric Operating System Firmware, Debian Debian Linux, Fedoraproject Fedora, Haxx Libcurl, Netapp Active Iq Unified Manager, Netapp Clustered Data Ontap, Netapp H300s Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H700s Firmware, Splunk Universal Forwarder.

## How do I fix CVE-2023-27538?

Upgrade to a fixed version.

## Is CVE-2023-27538 being exploited?

There is no known exploitation of CVE-2023-27538 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2023-27534](https://insights.sbomify.com/CVE-2023-27534/): Path traversal in https://github.com/curl/curl (high 8.8)
- [CVE-2021-4197](https://insights.sbomify.com/CVE-2021-4197/): Privilege escalation in kernel (high 7.8)
- [CVE-2021-27218](https://insights.sbomify.com/CVE-2021-27218/): Integer overflow in n/a (high 7.5)
- [CVE-2021-27219](https://insights.sbomify.com/CVE-2021-27219/): Integer overflow in n/a (high 7.5)
- [CVE-2019-19044](https://insights.sbomify.com/CVE-2019-19044/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-27538 and fix it if it is affected.

What it is: CVE-2023-27538 is a high-severity authentication bypass vulnerability in Debian Debian Linux, published on 30 Mar 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-27538 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2023-27538/ (Markdown: https://insights.sbomify.com/CVE-2023-27538/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-27538
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-27538
- OSV: https://osv.dev/vulnerability/CVE-2023-27538

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-27538/
Summaries are generated and may contain mistakes; the official description above is the record.