Home/CVE/Mbed TLS v3.3.0 up to 3.6.5 and 4.0.0 allows Algorithm Downgrade.
CVE

CVE-2026-25834

Mbed TLS v3.3.0 up to 3.6.5 and 4.0.0 allows Algorithm Downgrade.

Mbed TLS v3.3.0 up to 3.6.5 and 4.0.0 allows Algorithm Downgrade.

MEDIUM · CVSS 6.5 EPSS 0.00021
Schedule remediation
  • SSVC automatable: yes - attacks can be scripted at scale
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-295Improper Certificate Validation
CWE-327Use of a Broken or Risky Cryptographic Algorithm
▤

Affected Products & Versions

2
arm mbed tls>= 3.3.0 and < 3.6.6
arm mbed tlsall versions
▣

Scoring & Timeline

6.5
MEDIUM · CVSS v3.1 · cve@mitre.org
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD01 Apr 2026 · 06:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

4
suse-csafSUSE-SU-2026:1952-1
msrcCVE-2026-25834
suse-csafSUSE-SU-2026:21440-1
suse-csafopenSUSE-SU-2026:10498-1
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://mbed-tls.readthedocs.io/en/latest/security-advisories/Vendor Advisory
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-sigalg-injection/Vendor Advisory
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