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CVE-2026-34877

Arm Mbed Tls insecure deserialization

9.8 CRITICALEPSS 0.73%
  1. Published2 Apr 2026

Description

An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of serialized SSL context or session structures allows an attacker who can modify the serialized structures to induce memory corruption, leading to arbitrary code execution. This is caused by Incorrect Use of Privileged APIs.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Arm Mbed Tls≥ 2.19.0 < 3.6.6
Trustedfirmware Mbed Tls4.0.0

Remediation

Fixed in
Arm Mbed Tls≥ 3.6.6

References

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Frequently asked

Is CVE-2026-34877 being actively exploited?

CVE-2026-34877 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.73%.

How severe is CVE-2026-34877?

CVE-2026-34877 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.73% probability of exploitation.

Which products are affected by CVE-2026-34877?

Affected products include Arm Mbed Tls, Trustedfirmware Mbed Tls.

How do I fix CVE-2026-34877?

Upgrade affected software to a fixed version, for example Arm Mbed Tls 3.6.6 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-34877 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.