CVE-2026-34871: An issue was discovered in Mbed TLS before 3.6.6 and 4.x before 4.1.0 and TF-PSA-Crypto before 1.1.0

Q: How do I fix CVE-2026-34871?

mbed tls: upgrade to 3.6.6; tf-psa-crypto: upgrade to 1.1.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-34871 being exploited?

CVE-2026-34871 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-34871 affect?

CVE-2026-34871 affects mbed tls, tf-psa-crypto. Severity is medium (CVSS 6.7). An issue was discovered in Mbed TLS before 3.6.6 and 4.x before 4.1.0 and TF-PSA-Crypto before 1.1.0. There is a Predictable Seed in a Pseudo-Random Number Generator (PRNG).

Q: How urgent is CVE-2026-34871?

Priority 26/100. No elevated risk signals yet.

Routine

MEDIUM 6.7UPGRADEUPGRADE

CVE-2026-34871 is a medium-severity flaw (CVSS 6.7) affecting mbed tls, tf-psa-crypto. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in Mbed TLS before 3.6.6 and 4.x before 4.1.0 and TF-PSA-Crypto before 1.1.0. There is a Predictable Seed in a Pseudo-Random Number Generator (PRNG).

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.7 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 91%)
CISA exploited list	No
Weakness	CWE-338
Published	2026-04-01
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: arm · trustedfirmware

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-01 19:16 UTCPublished CVE record published
2026-06-17 10:39 UTCUpdated Record last modified

arm mbed tls UPGRADE

Affected: < 3.6.6

Fixed in: 3.6.6

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy mbed-tls || rpm -q mbed-tls || mbed-tls --version

2. UPGRADE to 3.6.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mbed-tls

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mbed-tls

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

trustedfirmware tf-psa-crypto UPGRADE

Affected: < 1.1.0

Fixed in: 1.1.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy tf-psa-crypto || rpm -q tf-psa-crypto || tf-psa-crypto --version

2. UPGRADE to 1.1.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade tf-psa-crypto

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tf-psa-crypto

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-34871?

mbed tls: upgrade to 3.6.6; tf-psa-crypto: upgrade to 1.1.0. Exact commands for each OS are on this page.

Is CVE-2026-34871 being exploited?

CVE-2026-34871 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-34871 affect?

CVE-2026-34871 affects mbed tls, tf-psa-crypto. Severity is medium (CVSS 6.7). An issue was discovered in Mbed TLS before 3.6.6 and 4.x before 4.1.0 and TF-PSA-Crypto before 1.1.0. There is a Predictable Seed in a Pseudo-Random Number Generator (PRNG).

How urgent is CVE-2026-34871?

Priority 26/100. No elevated risk signals yet.

Related CVEs

CVE-2026-34877 CRITICAL 9.8 UPGRADE DOWNGRADE An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0
CVE-2026-34876 HIGH 7.5 UPGRADE An issue was discovered in Mbed TLS 3.x before 3.6.6
CVE-2026-34875 CRITICAL 9.8 UPGRADE UPGRADE An issue was discovered in Mbed TLS through 3.6.5 and TF-PSA-Crypto 1.0.0
CVE-2026-34874 HIGH 7.5 UPGRADE An issue was discovered in Mbed TLS through 3.6.5 and 4.x through 4.0.0
CVE-2026-34873 CRITICAL 9.1 UPGRADE An issue was discovered in Mbed TLS 3.5.0 through 4.0.0

References

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