Executive brief
Mbed TLS is a widely used library that provides secure communication capabilities for embedded devices and applications. A vulnerability was identified where the library does not sufficiently protect internal session data when it is saved or restored. If an attacker can modify this saved data, they could cause the application to crash or potentially take control of the system, leading to a total compromise of the device's security and data.
Technical details
A vulnerability exists in Mbed TLS versions 2.19.0 through 3.6.5 and 4.0.0 due to the insecure deserialization of SSL context and session structures. The library provides APIs for applications to serialize TLS state for session resumption or caching but does not cryptographically sign or encrypt this data by default. If an attacker can modify the serialized buffer, the library may process malformed data structures during restoration, leading to out-of-bounds reads/writes or other memory corruption. While the vendor initially rated this as 'Low' due to the precondition of an attacker needing access to the serialized data, CISA-ADP has assigned a 'Critical' score (9.8) reflecting the potential for remote code execution if the storage mechanism is reachable. Documentation has been updated in versions 3.6.6 and 4.1.0 to mandate application-level integrity protection.
Affected products
- TrustedFirmware Mbed TLS 2.19.0 to 3.6.5, 4.0.0
Timeline
- 2026-03-31: advisory: Vendor advisory released
- 2026-04-02: disclosed: CVE published