FreeBSD : Mbed TLS -- Local side channel attack on classical CBC decryption in (D)TLS (4c69240f-f02c-11ea-838a-0011d823eebd)

medium Nessus Plugin ID 140312

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Synopsis

The remote FreeBSD host is missing a security-related update.

Description

Manuel Pegourie-Gonnard reports :

When decrypting/authenticating (D)TLS record in a connection using a CBC ciphersuite without the Encrypt-then-Mac extension RFC 7366, Mbed TLS used dummy rounds of the compression function associated with the hash used for HMAC in order to hide the length of the padding to remote attackers, as recommended in the original Lucky Thirteen paper.

A local attacker who is able to observe the state of the cache could monitor the presence of mbedtls_md_process() in the cache in order to determine when the actual computation ends and when the dummy rounds start. This is a reliable target as it's always called at least once, in response to a previous attack. The attacker can then continue with one of many well-documented Lucky 13 variants.

Solution

Update the affected package.

Plugin Details

Severity: Medium

ID: 140312

File Name: freebsd_pkg_4c69240ff02c11ea838a0011d823eebd.nasl

Version: 1.4

Type: local

Family: FreeBSD Local Security Checks

Published: 9/8/2020

Updated: 2/21/2024

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.6

CVSS v2

Risk Factor: Low

Base Score: 2.1

Temporal Score: 1.6

Vector: CVSS2#AV:L/AC:L/Au:N/C:P/I:N/A:N

CVSS Score Source: CVE-2020-16150

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:freebsd:freebsd:mbedtls, cpe:/o:freebsd:freebsd

Required KB Items: Host/local_checks_enabled, Host/FreeBSD/release, Host/FreeBSD/pkg_info

Exploit Ease: No known exploits are available

Patch Publication Date: 9/6/2020

Vulnerability Publication Date: 9/1/2020

Reference Information

CVE: CVE-2020-16150

Detections

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