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Fencer Vulns
high 7.5

CVE-2020-36478 json

An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS)

published 2021-08-23 5 y ago modified 2026-07-18 3 mo ago also EUVD-2020-23964 , JLSEC-2025-213

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia MbedTLS_jll 2.25.0+0
  • arm mbed_tls 2.7.18, 2.16.9, 2.25.0
  • siemens logo!_cmr2020_firmware 2.2
  • siemens logo!_cmr2040_firmware 2.2
  • mbedtls Debian 14, Debian 13, Debian 12 2.16.9-0.1

debian advisories DEBIAN-CVE-2020-36478

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-36478 updated cvss 9.1

mbedtls: NULL algorithm parameters entry looks identical to an array of REAL

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-21-257-20 updated cvss 7.5

Siemens LOGO! CMR and SIMATIC RTU 3000

  • Siemens LOGO! CMR2020 < 2.2 Siemens LOGO! CMR2040 < 2.2 Siemens SIMATIC RTU 3000 family
    affected: fixed in v2.2 support.industry.siemens.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

1.10% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/ARMmbed/mbedtls/issues/3629 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
julia MbedTLS_jll
<2.25.0+0
2.25.0+0

Classification

Weakness
  • CWE-295 Improper Certificate Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.