How severe is CVE-2020-36421?

CVE-2020-36421 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2020-36421 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-36421?

CVE-2020-36421 primarily affects Arm Mbed Tls. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-36421?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2020-36421 published?

CVE-2020-36421 was published on 2021-07-19 and last updated on 2026-06-17.

CVE-2020-36421

CVE-2020-36421 is a medium-severity vulnerability in Arm Mbed Tls with a CVSS 3.x base score of 5.3. 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-203.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 2% (73rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-203
Affected product: Arm Mbed Tls
Published: 2021-07-19
Last modified: 2026-06-17

Description

An issue was discovered in Arm Mbed TLS before 2.23.0. Because of a side channel in modular exponentiation, an RSA private key used in a secure enclave could be disclosed.

Frequently asked questions

What is CVE-2020-36421?: An issue was discovered in Arm Mbed TLS before 2.23.0. Because of a side channel in modular exponentiation, an RSA private key used in a secure enclave could be disclosed.
How severe is CVE-2020-36421?: CVE-2020-36421 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2020-36421 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-36421?: CVE-2020-36421 primarily affects Arm Mbed Tls. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-36421?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2020-36421 published?: CVE-2020-36421 was published on 2021-07-19 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

More vulnerabilities in Arm Mbed Tls

CVE-2026-34877 — Critical (CVSS 9.8): An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of…
CVE-2022-46393 — Critical (CVSS 9.8): An issue was discovered in Mbed TLS before 2.28.2 and 3.x before 3.3.0. There is a potential heap-based buffer overflow…
CVE-2021-44732 — Critical (CVSS 9.8): Mbed TLS before 3.0.1 has a double free in certain out-of-memory conditions, as demonstrated by an…
CVE-2017-18187 — Critical (CVSS 9.8): In ARM mbed TLS before 2.7.0, there is a bounds-check bypass through an integer overflow in PSK identity parsing in the…
CVE-2018-0488 — Critical (CVSS 9.8): ARM mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0, when the truncated HMAC extension and CBC are used, allows…
CVE-2018-0487 — Critical (CVSS 9.8): ARM mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0 allows remote attackers to execute arbitrary code or cause…

All CVEs affecting Arm Mbed Tls →

Other CWE-203 (Observable Discrepancy) vulnerabilities

CVE-2019-25337 — Critical (CVSS 9.8): OwnCloud 8.1.8 contains a username enumeration vulnerability that allows remote attackers to discover user accounts by…
CVE-2026-23519 — Critical (CVSS 9.8): RustCrypto CMOV provides conditional move CPU intrinsics which are guaranteed on major platforms to execute in…
CVE-2025-27667 — Critical (CVSS 9.8): Vasion Print (formerly PrinterLogic) before Virtual Appliance Host 22.0.843 Application 20.0.1923 allows Administrative…
CVE-2024-25714 — Critical (CVSS 9.8): In Rhonabwy through 1.1.13, HMAC signature verification uses a strcmp function that is vulnerable to side-channel…
CVE-2024-25191 — Critical (CVSS 9.8): php-jwt 1.0.0 uses strcmp (which is not constant time) to verify authentication, which makes it easier to bypass…
CVE-2024-25190 — Critical (CVSS 9.8): l8w8jwt 2.2.1 uses memcmp (which is not constant time) to verify authentication, which makes it easier to bypass…

Browse all CWE-203 (Observable Discrepancy) vulnerabilities →