CVE-2026-34871

Predictable cryptographic keys via early-boot entropy fallback

Published Apr 1, 2026 · Updated Apr 1, 2026

Predictable entropy in Mbed TLS 3.6.5 and earlier, Mbed TLS 4.0.0, and TF-PSA-Crypto 1.0.0 allows attackers to predict keys. When getrandom() is unavailable or blocked, entropy_poll.c and platform_util.c read /dev/urandom without waiting for the Linux entropy pool to initialize. Exposure requires installation or early boot without sufficient saved or hardware entropy; predictable keys and randomized ECDSA nonces can compromise generated keys.

CVSS severity6.7
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Predictable entropy in Mbed TLS 3.6.5 and earlier, Mbed TLS 4.0.0, and TF-PSA-Crypto 1.0.0 allows attackers to predict keys. When getrandom() is unavailable or blocked, entropy_poll.c and platform_util.c read /dev/urandom without waiting for the Linux entropy pool to initialize. Exposure requires installation or early boot without sufficient saved or hardware entropy; predictable keys and randomized ECDSA nonces can compromise generated keys.

The record

CVE
CVE-2026-34871
Published
Apr 1, 2026
Updated
Apr 1, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-338
Attack vector
local
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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.7CISA-ADPCVSS:3.1/AV:L/AC:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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