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libcurl CVE-2026-9546

| EUVDEUVD-2026-41494 HIGH
2026-06-24 GHSA-25rx-86v8-32c6
Information Disclosure Curl
7.5
CVSS 3.1 · Vendor
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Severity by source

Vendor (CNA) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
vuln.today AI
3.7 LOW

Leak depends on a specific handle-reuse-and-clear pattern (AC:H) and exposes only referrer strings to a third party (C:L); no integrity or availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
SUSE
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Primary rating from Vendor (CNA).

CVSS VectorVendor

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

5
Analysis Updated
Jul 06, 2026 - 18:39 vuln.today
v3 (cvss_changed)
Analysis Updated
Jul 06, 2026 - 18:39 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Jul 06, 2026 - 18:22 vuln.today
cvss_changed
CVSS changed
Jul 06, 2026 - 18:22 NVD
7.5 (HIGH)
Analysis Generated
Jun 24, 2026 - 18:26 vuln.today

Description PRE-NVD

Disclosed via oss-security. NVD scoring and full description are pending.

AnalysisAI

Information disclosure in libcurl (versions 8.18.0 through 8.20.0) causes the HTTP Referer header to persist on a reused easy handle even after an application explicitly clears it by passing NULL to CURLOPT_REFERER. Because the internal referrer state is not reset, a previously set referrer string is silently re-sent on later requests, potentially leaking sensitive URL data (paths, tokens, or query parameters) to unintended destination servers. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Set sensitive Referer on reused handle
Delivery
Clear referrer via CURLOPT_REFERER NULL
Exploit
Stale state not reset in libcurl
Execution
Referer re-sent to unintended server
Impact
Sensitive URL data disclosed in logs
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Vulnerability AssessmentAI

Exploitation Exploitation requires a specific application usage pattern, not a special attacker capability: the calling program must reuse the same libcurl easy handle across multiple requests, must have set a (sensitive) referrer on an earlier request, and must then attempt to suppress it by setting CURLOPT_REFERER to NULL on a subsequent request destined for a different server - at which point the stale referrer leaks. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The provided CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, base 7.5) rates this High, but that score overstates real-world risk and its metrics are debatable: the leak is not something a remote attacker directly triggers by sending traffic - it depends on the victim application reusing an easy handle and clearing the referrer, so effective attack complexity is higher and the confidentiality impact is closer to Low than High (only referrer strings leak, not arbitrary data). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An application uses a long-lived libcurl easy handle: for one request it sets a referrer containing a sensitive internal URL, then for a later request to a different, attacker-observed third-party host it sets CURLOPT_REFERER to NULL expecting no Referer header. Because the state is not cleared, the earlier sensitive referrer is transmitted to that third-party server, where an operator can read it from access logs. …
Remediation Upgrade libcurl to a fixed release above 8.20.0 as published in the curl security advisory at https://curl.se/docs/CVE-2026-9546.html; the input data does not contain an exact fixed version number, so confirm the patched version directly from that advisory rather than assuming one (patch available per vendor advisory, exact fix version not present in provided data). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

24 hours: Inventory all applications and systems using libcurl 8.18.0-8.20.0 via dependency scanning, SBOM review, and configuration audits. …

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Threat intelligence, references, and detailed analysis are available after sign-in.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SLES15-SP5-CHOST-BYOS-SAP-CCloud Not-Affected
SLES15-SP6-CHOST-BYOS Not-Affected
SLES15-SP6-CHOST-BYOS-Aliyun Not-Affected
SLES15-SP6-CHOST-BYOS-Azure Not-Affected
SLES15-SP6-CHOST-BYOS-EC2 Not-Affected

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CVE-2026-9546 vulnerability details – vuln.today
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