CVE-2026-9546A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared.
Updated under an hour ago ()
Does this affect you?
It affects haxx curl. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- Weakness (CWE)
- CWE-200
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
haxx curl haxx:curl | from 8.18.0 before 8.21.0 | NVD |
References
- https://curl.se/docs/CVE-2026-9546.htmlpatch, vendor-advisory
- https://curl.se/docs/CVE-2026-9546.jsonthird-party-advisory
- https://hackerone.com/reports/3754343exploit, issue-tracking, third-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.