Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-03T06:18:14 libcurl: libcurl: Information disclosure due to persistent Referer header 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N CWE-201

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.

A flaw was found in libcurl. This vulnerability causes the HTTP Referer header to persist even after it has been explicitly cleared. This can lead to the previous referrer string being unintentionally reused and sent in subsequent requests, potentially disclosing sensitive information to unintended servers.

Important: A flaw in libcurl allows for sensitive information disclosure. Despite attempts to explicitly clear the HTTP Referer header, its internal state persists, leading to the unintended reuse and transmission of previous referrer strings in subsequent requests. This could expose sensitive data to unintended third-party servers in Red Hat products and services that rely on libcurl for HTTP communications. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Red Hat Hardened Images 2026-06-24T00:00:00Z RHSA-2026:29017 curl-main-8.21.0-0.1.hum1 Red Hat Hardened Images 2026-07-02T00:00:00Z RHSA-2026:34975 rust-main-1.96.1-1.hum1 Red Hat Enterprise Linux 8 Not affected dotnet8.0 Red Hat JBoss Core Services Affected libcurl-1.dll Red Hat JBoss Core Services Affected libcurl.so https://www.cve.org/CVERecord?id=CVE-2026-9546 https://nvd.nist.gov/vuln/detail/CVE-2026-9546 https://curl.se/docs/CVE-2026-9546.html https://curl.se/docs/CVE-2026-9546.json https://hackerone.com/reports/3754343