CVE-2026-6276
stale custom cookie host causes cookie leak
7.5CVSSHIGH
Description
Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.
CVSS Vector Breakdown
Exploitability
AV:NAttack VectorNetwork
AC:LAttack ComplexityLow
PR:NPrivileges RequiredNone
UI:NUser InteractionNone
Scope
S:UScopeUnchanged
Impact
C:NConfidentialityNone
I:NIntegrityNone
A:HAvailabilityHigh
Weaknesses
Affected Products
Attack Graph
Products CVE Techniques Tactics
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Exploitability
Official Patch Available
MITRE ATT&CK
2 techniques Collection
Credential Access
References
https://curl.se/docs/CVE-2026-6276.json
curl.se
https://curl.se/docs/CVE-2026-6276.html
curl.se
https://hackerone.com/reports/3671818
hackerone.com
and 1 more references View all →
Timeline
Published
May 13, 2026
Last Updated
May 14, 2026
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