CVE-2026-9546

sending old referer

HIGH
7.5
CVSS Score
Published: July 3, 2026 at 06:18 AM UTC
Updated: September 15, 2026 at 07:35 AM UTC
1 product affected across 1 vendorCurl

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Severity
HIGH7.5
Exploit prediction
EPSS 0.7%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

8.18.0 ≤ v < 8.20.18.18.0 ≤ v < 8.21.02cb868242dc2ac9cd52ee64987ef51d5964a56f98.18.08.19.08.20.0
Vendor states this is fixed in 862e8a74a84478d82973471b4f49dc2746c1780e (fixed)
Affected range stops below 8.20.1, so it looks safe — our inference, not a vendor statement
Affected range stops below 8.21.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (3)

Third Party Advisory
Source: cverecord
https://curl.se/docs/CVE-2026-9546.json
PatchVendor Advisory
Source: cverecord
https://curl.se/docs/CVE-2026-9546.html
ExploitIssue TrackingThird Party Advisory
Source: cverecord
https://hackerone.com/reports/3754343

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
NVD-CWE-noinfoCWE-200

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