CVE-2026-9546

sending old referer

cve-program · severity unknownCVSS unknownCheck source for fixed versionsKEV status unknown

Original advisory

Historical advisory recorded 23 Oct 2026 15:48:27 UTC. Read the latest advisory.

cve-program · CVE-2026-9546

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-9546

Published

curl

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "curl",
                    "product": "curl",
                    "versions": [
                        {
                            "version": "8.18.0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "8.20.1"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

curl

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "curl",
                    "product": "curl",
                    "versions": [
                        {
                            "version": "2cb868242dc2ac9cd52ee64987ef51d5964a56f9",
                            "status": "affected",
                            "versionType": "git",
                            "lessThan": "862e8a74a84478d82973471b4f49dc2746c1780e"
                        }
                    ],
                    "defaultStatus": "unaffected",
                    "repo": "https://github.com/curl/curl.git"
                }

curl

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "curl",
                    "product": "curl",
                    "versions": [
                        {
                            "version": "8.20.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.19.0",
                            "status": "affected"
                        },
                        {
                            "version": "8.18.0",
                            "status": "affected"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

Original source record · Cite this exact observation · Complete original publisher JSON