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CVE-2026-9546— sending old referer

Quick assessment

Affected
curl curl
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

curl是瑞典cURL团队开源的一款用于从服务器传输数据或向服务器传输数据的工具。 curl存在信息泄露漏洞，该漏洞源于libcurl中HTTP 标头在明确清除时仍会持久化，当传递NULL给 时未能清除内部状态，导致前一referrer字符串错误地被重用并在后续请求中发送，可能将敏感信息泄露给非预期的服务器。

AI Predicted 5.3 Difficulty: Moderate EPSS 0.65% · P50

Possible ATT&CK Techniques 1 AI

T1041 · Exfiltration Over C2 Channel

Affected Version Matrix 5

VendorProduct Version RangeStatus
curl curl 8.18.0< 8.20.1 affected
2cb868242dc2ac9cd52ee64987ef51d5964a56f9< 862e8a74a84478d82973471b4f49dc2746c1780e affected
8.20.0 affected
8.19.0 affected
8.18.0 affected
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I. Basic Information for CVE-2026-9546

Vulnerability Information
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Vulnerability Title
sending old referer
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
curl 信息泄露漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
curl是瑞典cURL团队开源的一款用于从服务器传输数据或向服务器传输数据的工具。 curl存在信息泄露漏洞，该漏洞源于libcurl中HTTP `Referer:`标头在明确清除时仍会持久化，当传递NULL给`CURLOPT_REFERER`时未能清除内部状态，导致前一referrer字符串错误地被重用并在后续请求中发送，可能将敏感信息泄露给非预期的服务器。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
curl curl 8.18.0 ~ 8.20.1 -
curl curl 2cb868242dc2ac9cd52ee64987ef51d5964a56f9 ~ 862e8a74a84478d82973471b4f49dc2746c1780e -
curl curl 8.20.0 -

II. Public POCs for CVE-2026-9546

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III. Intelligence Information for CVE-2026-9546

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Vendor Advisories for CVE-2026-9546 (1)

Other References for CVE-2026-9546 (2)

Same Patch Batch · curl · 2026-07-03 · 18 CVEs total

CVE-2026-10536 HTTP/2 stream-dependency tree UAF
CVE-2026-8932 incomplete mTLS config matching in conn reuse
CVE-2026-8458 wrong reuse for different services
CVE-2026-8925 SASL double-free
CVE-2026-8286 wrong STARTTLS connection reuse
CVE-2026-8927 env-set cross-proxy Digest auth state leak
CVE-2026-8926 password leak with netrc and user in URL
CVE-2026-8924 trailing dot domain super cookie
CVE-2026-12064 proto-default skips SSH verification
CVE-2026-11352 QUIC zero-length UDP datagrams busy-loop
CVE-2026-9545 exposing HTTP/3 early data
CVE-2026-9080 UAF after pause in socket callback
CVE-2026-9547 SSH improper host validation
CVE-2026-9079 stale proxy password leak
CVE-2026-11564 Native CA trust persist
CVE-2026-11856 cross-origin Digest auth state leak
CVE-2026-11586 WS Auto-PONG memory exhaustion

IV. Related Vulnerabilities

Same product: curl
Same vendor: curl
Same weakness: CWE-200

V. Comments for CVE-2026-9546

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