CVE-2026-34872Network attack vector

Constrained shared secrets via unchecked FFDH peer keys

Published Apr 1, 2026 · Updated Apr 1, 2026

Improper FFDH key validation in Mbed TLS 3.6.5 and earlier and TF-PSA-Crypto 1.0.0 allows remote attackers to constrain shared secrets. The built-in PSA driver accepts peer public keys without the range validation required for PSA_ALG_FFDH, letting a peer force the result into a small value set. Only PSA API applications using FFDH in a protocol that requires contributory behavior are affected; TLS and legacy mbedtls_dhm_calc_secret() use are not.

CVSS severity9.1
Critical
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper FFDH key validation in Mbed TLS 3.6.5 and earlier and TF-PSA-Crypto 1.0.0 allows remote attackers to constrain shared secrets. The built-in PSA driver accepts peer public keys without the range validation required for PSA_ALG_FFDH, letting a peer force the result into a small value set. Only PSA API applications using FFDH in a protocol that requires contributory behavior are affected; TLS and legacy mbedtls_dhm_calc_secret() use are not.

The record

CVE
CVE-2026-34872
Published
Apr 1, 2026
Updated
Apr 1, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-347, T1600
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1600Weaken Encryption

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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