{"id":"CVE-2026-9546","title":"A vulnerability in libcurl caused the HTTP `Referer:` header to persist even\nwhen explicitly cleared","summary":"A vulnerability in libcurl caused the HTTP `Referer:` header to persist even\nwhen explicitly cleared. While the documentation states that passing NULL to\n`CURLOPT_REFERER` suppresses the header, the option failed to clear the\ninternal st…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","cwe":["CWE-200","CWE-201"],"vendor":"haxx","product":"curl","affected":["curl >= 8.18.0, < 8.21.0"],"patched":["curl 8.21.0"],"published":"2026-07-03","updated":"2026-09-15","sourceUpdated":"2026-09-15T07:16:35.130","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-9546","references":[{"url":"https://curl.se/docs/CVE-2026-9546.html","label":"2499f714-1537-4658-8207-48ae4bb9eae9"},{"url":"https://curl.se/docs/CVE-2026-9546.json","label":"2499f714-1537-4658-8207-48ae4bb9eae9"},{"url":"https://hackerone.com/reports/3754343","label":"2499f714-1537-4658-8207-48ae4bb9eae9"},{"url":"https://hackerone.com/reports/3754343","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-9546.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-9546"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2496770"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-9546"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-9546"},{"url":"https://access.redhat.com/errata/RHSA-2026:34975"},{"url":"https://access.redhat.com/errata/RHSA-2026:29017"}],"tags":["nvd","cve.org","exploit-available","csaf","vex","red-hat"],"exploitAvailable":true,"ssvc":{"exploitation":"poc","automatable":"yes","technicalImpact":"partial","timestamp":"2026-07-06T16:51:06.094113Z"},"epss":0.00652,"epssPercentile":0.51039,"ingestedAt":"2026-07-04T06:55:48.805Z","slug":"CVE-2026-9546","body":"## Overview\n\nA vulnerability in libcurl caused the HTTP `Referer:` header to persist even\nwhen explicitly cleared. While the documentation states that passing NULL to\n`CURLOPT_REFERER` suppresses the header, the option failed to clear the\ninternal state. As a result, the previous referrer string was erroneously\nreused and sent in subsequent requests, potentially leaking sensitive\ninformation to unintended servers.\n\n## Affected\n\n- `curl >= 8.18.0, < 8.21.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `curl 8.21.0`\n\n## Vendor advisories\n\n- **RHSA-2026:34975** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-07-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:34975)\n- **RHSA-2026:29017** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-06-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:29017)\n- **Red Hat VEX** · Moderate · affected: Confidential Compute Attestation, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · no fix planned: Confidential Compute Attestation, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, … · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-9546.json)","depth":"midnight","depthScore":53,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[{"seq":203515,"id":"CVE-2026-9546","ts":1789457645883,"field":"exploit_available","old":"false","new":"true"},{"seq":203514,"id":"CVE-2026-9546","ts":1789457645883,"field":"cvss","old":null,"new":"7.5"},{"seq":203513,"id":"CVE-2026-9546","ts":1789457645883,"field":"severity","old":"none","new":"high"}]}