CVE-2026-9546

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.

Database specific

{
    "cna_assigner": "curl",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/9xxx/CVE-2026-9546.json",
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "introduced": "8.20.0"
                },
                {
                    "last_affected": "8.20.0"
                },
                {
                    "introduced": "8.19.0"
                },
                {
                    "last_affected": "8.19.0"
                },
                {
                    "introduced": "8.18.0"
                },
                {
                    "last_affected": "8.18.0"
                }
            ]
        }
    ]
}

References

Affected packages

Git / github.com/curl/curl

Affected ranges

Type

GIT

Repo

https://github.com/curl/curl

Events

Introduced

2eebc58c4b8d68c98c8344381a9f6df4cca838fd

Fixed

68720b4837284335b2d63cb358f8f6ce65f5bc55

Database specific

{
    "cpe": "cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*",
    "source": "CPE_RANGE",
    "extracted_events": [
        {
            "introduced": "8.18.0"
        },
        {
            "fixed": "8.21.0"
        }
    ]
}

Affected versions

Other

curl-8_18_0

curl-8_19_0

curl-8_20_0

rc-8_20_0-1

rc-8_20_0-2

rc-8_20_0-3

rc-8_21_0-1

rc-8_21_0-2

rc-8_21_0-3

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-9546.json"