Cyber Resilience

CVE-2026-25834

Crypto Weakness in Trustedfirmware Mbed Tls 3.3.0 – 3.6.6

Crypto Weakness
Published
01 April 2026
Modified
05 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 6.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
EPSS Score 0.0014 3th percentile
Risk Priority 48 floored blend · peak EPSS

Summary

CVE-2026-25834 is a medium-severity Improper Certificate Validation (CWE-295) vulnerability in Trustedfirmware Mbed Tls. Its CVSS base score is 6.5 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Adversary-in-the-Middle (T1557); ranked at the 3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SC-13 (Cryptographic Protection) and SC-17 (Public Key Infrastructure Certificates) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A04:2025 Cryptographic FailuresA07:2025 Authentication Failures

EU & UK References

Vulnerability Data

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

CWE(s)
CWE-295CWE-327

Related Threats

MITRE ATT&CK Enterprise Techniques

T1557 Adversary-in-the-Middle Credential Access
Adversaries may attempt to position themselves between two or more networked devices using an adversary-in-the-middle (AiTM) technique to support follow-on behaviors such as [Network Sniffing](https://attack.
attack.mitre.org →
T1557.002 ARP Cache Poisoning Credential Access
Adversaries may poison Address Resolution Protocol (ARP) caches to position themselves between the communication of two or more networked devices.
attack.mitre.org →
T1557.003 DHCP Spoofing Credential Access
Adversaries may redirect network traffic to adversary-owned systems by spoofing Dynamic Host Configuration Protocol (DHCP) traffic and acting as a malicious DHCP server on the victim network.
attack.mitre.org →
T1557.004 Evil Twin Credential Access
Adversaries may host seemingly genuine Wi-Fi access points to deceive users into connecting to malicious networks as a way of supporting follow-on behaviors such as [Network Sniffing](https://attack.
attack.mitre.org →
T1040 Network Sniffing Credential Access
Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-45159Same product: Trustedfirmware Mbed Tls
CVE-2024-28755Same product: Trustedfirmware Mbed Tls
CVE-2026-34873Same product: Trustedfirmware Mbed Tls
CVE-2026-25833Same product: Trustedfirmware Mbed Tls
CVE-2026-34874Same product: Trustedfirmware Mbed Tls
CVE-2026-34876Same product: Trustedfirmware Mbed Tls
CVE-2025-49601Same product: Trustedfirmware Mbed Tls
CVE-2024-45157Same product: Trustedfirmware Mbed Tls
CVE-2023-45199Same product: Trustedfirmware Mbed Tls
CVE-2024-28836Same product: Trustedfirmware Mbed Tls

Affected Assets

trustedfirmware
mbed tls
4.0.0 · 3.3.0 — 3.6.6

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 18 hardening rules · 8 OS baselines
Validate
Prove the fix (OWASP ASVS)

—

Mitigating Controls (NIST 800-53 r5) AI

SC-13 Cryptographic Protection good match

SC-13 requires selection and implementation of specific cryptography types, directly stopping use of broken algorithms.

SC-17 Public Key Infrastructure Certificates good match

PKI certificate issuance and acquisition under an approved policy establishes the trusted roots and processes needed for correct validation.

SC-23 Session Authenticity partial match

Protecting session authenticity depends on cryptographic mechanisms whose trust depends on correct certificate validation.

SC-8 Transmission Confidentiality and Integrity partial match

Requiring confidentiality and integrity protection of transmitted data drives use of properly validated certificates in protocols such as TLS.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-03 mostly match
prevents

Certificate-based authentication of users/services/hardware directly depends on correct validation.

PR.DS-02 mostly match
prevents

Proper certificate validation is a core mechanism for protecting data-in-transit confidentiality and integrity.

PR.PS-06 mostly match
prevents

Secure development practices explicitly include implementing correct certificate validation logic.

ID.RA-09 partial match
prevents

Assessing authenticity/integrity of acquired software often relies on code-signing certificate validation.

PR.AA-04 partial match
prevents

Identity assertions conveyed via certificates require validation to be verified.

PR.DS-01 partial match
prevents

PR.DS-01 promotes encryption for data-at-rest but never requires strong algorithms, leaving CWE-327 fully possible; the weakness is also far broader than data-at-rest so one narrow control removes none of its total risk.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.24 Use of cryptography mostly match
prevents

Mandating approved algorithms, cipher strength and usage standards directly stops the selection of broken or weak cryptographic primitives that attackers can exploit.

A.5.31 Legal, statutory, regulatory and contractual requirements partial match
prevents

The explicit call-out of cryptography-related legal constraints (import/export, key escrow, digital-signature validity) reduces the likelihood that an organization will adopt broken or non-compliant cryptographic algorithms that violate those rules.

A.5.6 Contact with special interest groups partial match
prevents

Access to current specialist guidance and early vulnerability alerts enables timely replacement of broken or risky cryptographic algorithms with stronger alternatives.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (4 rules)
  • V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-295
  • V-248524 OL 8 must implement NIST FIPS-validated cryptography for the following: To provision digital signatures, to generate cryptographic hashes, and to protect data requiring data-at-rest protections in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards. prevents CWE-327
  • V-248531 OL 8, for PKI-based authentication, must validate certificates by constructing a certification path (which includes status information) to an accepted trust anchor. prevents CWE-295
RHEL 7 (2 rules)
  • V-204447 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
  • V-204448 The Red Hat Enterprise Linux operating system must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
RHEL 8 (2 rules)
  • V-230264 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
  • V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-295
Windows 10 (1 rule)
  • V-220937 The system must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows 11 (1 rule)
  • V-253461 The system must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows Server 2016 (1 rule)
  • V-225053 Windows Server 2016 must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows Server 2019 (1 rule)
  • V-205654 Windows Server 2019 must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327
Windows Server 2022 (1 rule)
  • V-254474 Windows Server 2022 must be configured to prevent the storage of the LAN Manager hash of passwords. prevents CWE-327

References