CVE-2026-34877
A critical flaw in the Mbed TLS library allows attackers to modify serialized SSL context or session data, causing memory corruption and arbitrary code execution. The vulnerability exists in versions 2.19.0 through 3.6.5 and 4.0.0. It can be exploited remotely without authentication or user interaction.
No official fix yet. If none appears within 45 days of first tracking, this entry is removed automatically.
Who is affected
Mbed TLS library versions 2.19.0 to 3.6.5 and 4.0.0, used in ARM Mbed TLS and Trusted Firmware products.
Real-world impact
An attacker who can tamper with serialized SSL data can corrupt memory and run arbitrary code, potentially taking full control of the affected device.
Why this severity
The CVSS score of 9.8 reflects that the vulnerability can be exploited remotely without authentication or user interaction, and leads to complete compromise of confidentiality, integrity, and availability.
What to do about it
No official fix or mitigation is documented in the sources yet. Monitor the vendor advisory and apply the patch as soon as it is released.
No fix documented in sources
Timeline
- Apr 2, 2026 · Apr 2, 2026PublishedDisclosed and added to the National Vulnerability Database.
- Jul 24, 2026 · 12d agoAdvisory updatedThe NVD record was last revised.
How it’s attacked
References & advisories
- mbed-tls.readthedocs.io/en/latest/security-advisori…vendor advisory
- mbed-tls.readthedocs.io/en/latest/security-advisori…vendor advisory