# CVE-2026-8932: curl libcurl authentication bypass via improper mTLS connection reuse

Source: https://junglewise.ai/threats/cve-2026-8932-curl-libcurl-authentication-bypass-via-improper-mtls-connection  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-03. Updated: 2026-07-03  
License: CC BY 4.0 with a link back

CVE-2026-8932 · Severity: info · Published 2026-07-03

libcurl, a widely used library for transferring data over various protocols, contains a flaw in how it manages secure connections. When an application attempts to establish a new secure connection using different client certificate settings (mTLS), libcurl may incorrectly reuse an existing connection that was established with different credentials. This could lead to an authentication bypass where a request is sent using the wrong identity, potentially exposing sensitive data or performing unauthorized actions.

## Quick answers

**Is CVE-2026-8932 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-8932 being exploited in the wild.

**How severe is CVE-2026-8932?** Informational severity, published 3 July 2026.

**Which products and versions are affected?** curl libcurl 7.7 to 8.20.0.

**Is there a fix for CVE-2026-8932?** A patch was published on 2026-06-24: Fixed in curl version 8.21.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-8932 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-8932?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in libcurl's connection reuse logic (CWE-305). libcurl maintains a pool of previously used connections to optimize performance; however, the logic responsible for matching a new request to an existing connection failed to account for certain TLS settings related to client certificates and private keys. Consequently, libcurl may reuse a connection for a transfer that should have required different mTLS credentials. This issue affects libcurl but not the curl command-line tool. The vulnerability is resolved in version 8.21.0 by ensuring all relevant mTLS configuration options are included in the connection matching checks.

## Affected products

- curl libcurl 7.7 to 8.20.0

## Timeline

- 2026-05-13: disclosed: Reported to the curl project via HackerOne.
- 2026-06-24: patched: Fixed in curl version 8.21.0.
- 2026-06-24: advisory: Project curl security advisory published.

## References

- [https://curl.se/docs/CVE-2026-8932.html](https://curl.se/docs/CVE-2026-8932.html)
- [https://curl.se/docs/CVE-2026-8932.json](https://curl.se/docs/CVE-2026-8932.json)
- [https://hackerone.com/reports/3733910](https://hackerone.com/reports/3733910)