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CVE-2026-9546

sending old referer

High7.5EPSS 0.65%
Published
Updated
Reserved
Assigned by
curl

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.

Scores

CVSS scores of CVE-2026-9546, by who scored it
Scored byCVSSScoreVector
CISA-ADPADP (enrichment)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVDNVD · Modified3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (exploitation in 30 days)
0.65% · top 49% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: poc · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

Affected products

  • curl · curl

    • affected 8.18.0 – < 8.20.1

  • curl · curl

    • affected 2cb868242dc2ac9cd52ee64987ef51d5964a56f9 – < 862e8a74a84478d82973471b4f49dc2746c1780e

  • curl · curl

    • affected 8.20.0
    • affected 8.19.0
    • affected 8.18.0

References (3)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .