CVE-2020-36478

Exp

An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS). A NULL algorithm parameters entry looks identical to an array of REAL (size zero) and thus the certificate is considered valid. However, if the parameters do not match in any way, then the certificate should be considered invalid.

Published: 2021-08-22 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-36478 is rated High Exploit Risk (67.4/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.18%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2020-36478

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2020-36478

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-28 1.10% 1.18% +0.08%
2 2026-06-15 0.52% 1.10% +0.58%
3 2026-01-12 — 0.52% —

Full EPSS history (20 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-36478

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2020-36478

OS Trackers for CVE-2020-36478

vendor priority summary link
debian not yet assigned CVE-2020-36478 not yet assigned priority: Debian including 1 source packages (mbedtls), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-36478
gentoo normal CVE-2020-36478: 1 GLSA(s) (202301-08), 1 atom(s) (net-libs/mbedtls); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-36478
ubuntu medium CVE-2020-36478 medium priority: Ubuntu including 1 source packages (mbedtls), 15 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 10, needs-triage 3, DNE 1, released 1. https://ubuntu.com/security/CVE-2020-36478

Affected software / configurations for CVE-2020-36478

Vendor Product Version Raw CPE
arm mbed_tls < 2.7.18 cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
arm mbed_tls >= 2.8.0, < 2.16.9 cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
arm mbed_tls >= 2.17.0, < 2.25.0 cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
siemens logo\!_cmr2020_firmware < 2.2 cpe:2.3:o:siemens:logo\!_cmr2020_firmware:*:*:*:*:*:*:*:*
siemens logo\!_cmr2040_firmware < 2.2 cpe:2.3:o:siemens:logo\!_cmr2040_firmware:*:*:*:*:*:*:*:*
siemens simatic_rtu3031c_firmware — cpe:2.3:o:siemens:simatic_rtu3031c_firmware:*:*:*:*:*:*:*:*
siemens simatic_rtu3041c_firmware — cpe:2.3:o:siemens:simatic_rtu3041c_firmware:*:*:*:*:*:*:*:*
siemens simatic_rtu3030c_firmware — cpe:2.3:o:siemens:simatic_rtu3030c_firmware:*:*:*:*:*:*:*:*
siemens simatic_rtu3000c_firmware — cpe:2.3:o:siemens:simatic_rtu3000c_firmware:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

References for CVE-2020-36478

cvelogic Threat Intelligence