Bug 2541660 (CVE-2026-91768)

Summary: CVE-2026-91768 php: php: Access control bypass via partial IPv6 address comparison
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in PHP. The access control check for Internet Protocol version 6 (IPv6) addresses in the FastCGI implementation compares only the first 12 bytes of a 16-byte address instead of the complete address. An attacker on an adjacent network with an address sharing the first 96 bits with an authorized client can bypass network access restrictions to reach the FastCGI endpoint, potentially leading to unauthorized information disclosure.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-25 21:21:47 UTC 
The IPv6 branch of the FastCGI client access check compares only the first 12 bytes of a 16-byte IPv6 address, so listen.allowed_clients matches on a /96 prefix instead of the exact address. An attacker who can source an address sharing the first 96 bits with an allowed one passes the check and reaches the FastCGI endpoint.