CVE-2026-9546
A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.49%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- EPSS
- 0.49% probability · 41th percentile
- CISA KEV
- Not listed
- Affected
- haxx/curl
- Source
- 2499f714-1537-4658-8207-48ae4bb9eae9
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
- https://hackerone.com/reports/3754343Exploit, Issue Tracking, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.