NVD / CVE Program· CNA mitre

CVE-2020-36477: An issue was discovered in Mbed TLS before 2.24.0.

MediumCVSS 5.9 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 23/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.86% (FIRST EPSS); higher than 58.9% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
Fixed version: mbedtls (Debian:12) 2.28.0-0.3.

Low priority for now. Upgrade to mbedtls (Debian:12) 2.28.0-0.3 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

An issue was discovered in Mbed TLS before 2.24.0. The verification of X.509 certificates when matching the expected common name (the cn argument of mbedtls_x509_crt_verify) with the actual certificate name is mishandled: when the subjecAltName extension is present, the expected name is compared to any name in that extension regardless of its type. This means that an attacker could impersonate a 4-byte or 16-byte domain by getting a certificate for the corresponding IPv4 or IPv6 address (this would require the attacker to control that IP address, though).

BDU:2022-01651

Published: Aug 22, 2021
Updated: Jun 16, 2026
EPSS: 0.8% · 58th percentile
CWE: CWE-295

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 23 / 40 · 5.9 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.8%

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No public exploit code on record
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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

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Vendor	Product	CPE
arm	mbed tls	cpe:2.3:a:arm:mbed_tls

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The Mbed TLS version can't be seen from outside; the free SSL checker tests your certificate, enabled TLS versions and weak ciphers. Confirm the version on your server with the package manager.

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

arm mbed tlsbefore 2.24.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	mbedtls	before 2.28.0-0.3	2.28.0-0.3

Same product

arm: all records

Other highest-scoring records for the same primary product.

CVE-2025-47917Mbed TLS before 3.6.4 allows a use-after-free in certain situations of applications that are developed in accordance with the documentation.
40Plan
CVE-2021-44732Mbed TLS before 3.0.1 has a double free in certain out-of-memory conditions, as demonstrated by an mbedtls_ssl_set_session() failure.
40Plan
CVE-2017-18187In ARM mbed TLS before 2.7.0, there is a bounds-check bypass through an integer overflow in PSK identity parsing in the…
40Plan

Published before and after this one in the same product

← EarlierCVE-2020-36475Aug 22, 2021 · An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS).
31Monitor
← EarlierCVE-2020-36476Aug 22, 2021 · An issue was discovered in Mbed TLS before 2.24.0 (and before 2.16.8 LTS and before 2.7.17 LTS).
30Monitor
Later →CVE-2020-36478Aug 22, 2021 · An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS).
30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
debian:mbedtls	2.28.0-0.3 · Debian:12	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Bug bounty scope

ArmIntigriti · paid · up to $20,000

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
Special conditions such as timing or configuration are required.

If successful

Confidentiality: none
Integrity: high · data or configuration can be modified
Availability: none

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: High
Availability impact: None

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

nvd-primary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin

1override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {
2  // Left empty for the test environment
3}

Fixed

kotlin

1val client = OkHttpClient.Builder()
2  .certificatePinner(
3    CertificatePinner.Builder()
4      .add("api.sirius.example", "sha256/…")
5      .build()
6  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:48 PM UTC

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References

github.com/ARMmbed/mbedtls/issues/3498

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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