CVE-2026-9546
CVE-2026-9546 is a high-severity vulnerability in Haxx Curl with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.
Key facts
- Severity: High (CVSS 3.x base score 7.5)
- EPSS exploit prediction: 0% (39th percentile)
- Actively exploited: Not listed in CISA KEV
- Affected product: Haxx Curl
- Published:
- Last modified:
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.
Frequently asked questions
- What is 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.
- How severe is CVE-2026-9546?
- CVE-2026-9546 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
- Is CVE-2026-9546 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-9546?
- CVE-2026-9546 affects Haxx Curl. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-9546?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2026-9546 published?
- CVE-2026-9546 was published on 2026-07-03 and last updated on 2026-07-07.
References
- https://curl.se/docs/CVE-2026-9546.html
- https://curl.se/docs/CVE-2026-9546.json
- https://hackerone.com/reports/3754343
Affected products (1)
- cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*
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