Summary
FL MGUARD and TC MGUARD devices are affected by a possible infinite loop within a OpenSSL library method for parsing elliptic curve parameters. This method is used on parsing cryptographic certificates that contain elliptic curve public keys in compressed form, which may occur on:
Parsing client certificates for HTTPS administrative login
Parsing client certificates for SSH administrative login
Parsing peer certificates for IPsec VPN connections
Parsing certificates of external servers, including:
OpenVPN server
Configuration pull server
Update server
Attackers could try to exploit the vulnerability from remote.
For the mGuard Device Manager only the mdm Installer for Windows is affected.
UPDATE A: Added FL MGUARD 1102 and FL MGUARD 1105:
On FL MGUARD 1102 and FL MGUARD 1105 with mGuardNT 1.5.2 and older, the device can
be affected through an adapted certificate. This can occur on connection with a remote logging
server, configured for certificate authentication, or an remote authentication server at certificate
based authentication.
Details
Impact
By sending a crafted certificate, attackers may trigger an infinite loop in the receiving service. This may cause the service to become unavailable. Additionally, the availability of other services may be reduced due to high CPU load.
FL MGUARD and TC MGUARD may be vulnerable in the following setups:
- Activated HTTPS administrative access with certificate-based authentication
- Activated SSH administrative access with certificate-based authentication
Use of IPsec VPN connections with certificate-based authentication
- Use of connections to external servers with certificate-based authentication, including:
1. OpenVPN server
2. Configuration pull server
3. Update server
FL WLAN may be vulnerable in the following setup:
- WLAN Client modes with activated certificate-based RADIUS server authentication
The services can be vulnerable, even when they are not configured to use elliptic curve cryptography explicitly.
Mitigation
To reduce the possibility of an attack, affected functionality could be deactivated or used only in a way that it is not exposed on untrusted interfaces.
Remediation
This vulnerability is fixed in firmware version 8.8.6. We strongly recommend all affected FL MGUARD and TC MGUARD users to upgrade to this or a later version.
PHOENIX CONTACT strongly recommends upgrading FL MGUARD DM UNLIMITED to version 1.13.0.2 or higher, which fixes this vulnerability.
For FL WLAN devices the vulnerability will be fixed in the next regular release. A release date is not yet defined.
Vulnerabilities 1
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High 7.5
Infinite loop in BN_mod_sqrt() reachable when parsing certificates
The BN_mod_sqrt() function, which computes a modular square root, contains a bug that can cause it to loop forever for non-prime moduli. Internally this function is used when parsing certificates that contain elliptic curve public keys in compressed form or e…
Revision history
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#3
Fix: added distribution
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#2
Update A
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#1
Initial revision.
References
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PHOENIX CONTACT PSIRT
https://phoenixcontact.com/psirt
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CERT@VDE Security Advisories for PHOENIX CONTACT
https://certvde.com/en/advisories/vendor/phoenixcontact/
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VDE-2022-013: PHOENIX CONTACT: Multiple products affected by possible infinite loop within OpenSSL library - HTML
https://certvde.com/en/advisories/VDE-2022-013/