# CVE-2026-9546: curl: A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared

CVE-2026-9546 is fixed in curl on 1 platform, first by DEBIAN-CVE-2026-9546, released July 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-9546
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0065
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 3, 2026

## Description

A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared. While the documentation states that passing NULL to `CURLOPT_REFERER` suppresses the header, the option failed to clear the internal state. As a result, the previous referrer string was erroneously reused and sent in subsequent requests, potentially leaking sensitive information to unintended servers.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | curl Debian 14 | 8.21.0~rc2-1 | [DEBIAN-CVE-2026-9546](https://patchblox.com/security/data/fix/linux/debian-cve-2026-9546.md) | Jul 24, 2026 |
| Linux | curl sles 15.6 | 8.22.0-150600.4.58.1 | [SUSE-SU-2026:5069-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5069-1.md) | Nov 7, 2026 |
| Linux | curl sles 15.7 | 8.22.0-150700.7.33.1 | [SUSE-SU-2026:5068-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5068-1.md) | Nov 7, 2026 |

---

Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.