How severe is CVE-2018-1000520?

CVE-2018-1000520 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2018-1000520 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-1000520?

CVE-2018-1000520 affects Arm Mbed Tls. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-1000520?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2018-1000520 published?

CVE-2018-1000520 was published on 2018-06-26 and last updated on 2026-06-17.

CVE-2018-1000520

CVE-2018-1000520 is a high-severity vulnerability in Arm Mbed Tls with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-295.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (49th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Arm Mbed Tls
Published: 2018-06-26
Last modified: 2026-06-17

Description

ARM mbedTLS version 2.7.0 and earlier contains a Ciphersuite Allows Incorrectly Signed Certificates vulnerability in mbedtls_ssl_get_verify_result() that can result in ECDSA-signed certificates are accepted, when only RSA-signed ones should be.. This attack appear to be exploitable via Peers negotiate a TLS-ECDH-RSA-* ciphersuite. Any of the peers can then provide an ECDSA-signed certificate, when only an RSA-signed one should be accepted..

Frequently asked questions

What is CVE-2018-1000520?: ARM mbedTLS version 2.7.0 and earlier contains a Ciphersuite Allows Incorrectly Signed Certificates vulnerability in mbedtls_ssl_get_verify_result() that can result in ECDSA-signed certificates are accepted, when only RSA-signed ones should be.. This attack appear to be exploitable via Peers negotiate a TLS-ECDH-RSA-* ciphersuite. Any of the peers can then provide an ECDSA-signed certificate, when only an RSA-signed one should be accepted..
How severe is CVE-2018-1000520?: CVE-2018-1000520 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2018-1000520 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-1000520?: CVE-2018-1000520 affects Arm Mbed Tls. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-1000520?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2018-1000520 published?: CVE-2018-1000520 was published on 2018-06-26 and last updated on 2026-06-17.

References

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

Affected products (1)

cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*

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