CVE-2018-0488

Vulnerability

A heap corruption vulnerability exists in ARM mbed TLS when the truncated HMAC extension and CBC cipher mode are used together. The flaw allows a remote attacker to craft a malicious application packet within a TLS or DTLS session, causing a bounds-check bypass via an integer overflow that leads to heap corruption. Affected versions are mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0 [1][2].

Exploitation

An attacker must be in a position to send a crafted application packet to a target using mbed TLS with the truncated HMAC extension and CBC enabled within a TLS or DTLS session. No prior authentication is required; the attack is remote. The specific sequence involves injecting a malicious packet that triggers an integer overflow during HMAC processing, leading to a heap buffer overflow [1].

Impact

Successful exploitation allows the attacker to achieve remote code execution with the privileges of the affected process or cause a denial of service via heap corruption. The compromise can lead to full control of the TLS session or application [1][2].

Mitigation

Fixed versions are mbed TLS 1.3.22, 2.1.10, and 2.7.0, released on or before 2018-02-13. Users should upgrade to these or later versions. For Ubuntu systems, update mbedtls per USN-4267-1 [1]; for Gentoo, upgrade to >=net-libs/mbedtls-2.7.2 [2]. No workaround is available if an upgrade cannot be applied.