#VU14538 Improper certificate validation in mbed TLS - CVE-2018-1000520

Vulnerability identifier: #VU14538

Vulnerability risk: Low

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2018-1000520

CWE-ID: CWE-295

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
mbed TLS
Universal components / Libraries / Libraries used by multiple products

Vendor: ARM

Description

The vulnerability allows a remote attacker to bypass security restrictions on the target system.

The vulnerability exists in the mbedtls_ssl_get_verify_result() function of ARM mbed Transport Layer Security (TLS) due to improper validation of signed certificates. A remote attacker on a peer system can use a negotiated cipher suite of an Elliptic Curve Diffie-Hellman (ECDH) key exchange and Rivest-Shamir-Adleman (RSA) signed certificate (TLS-ECDH-RSA-*) to cause the targeted system to accept an arbitrary ECDSA signed certificate.

Mitigation
Install update from vendor's website.

Vulnerable software versions

mbed TLS: 1.3.0 - 1.3.22, 2.1.0 - 2.1.14, 2.4.0 - 2.4.2, 2.7.0

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External links
https://github.com/ARMmbed/mbedtls/issues/1561

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.