CVE-2019-1559

Description

If an application encounters a fatal protocol error and then calls SSL_shutdown() twice (once to send a close_notify, and once to receive one) then OpenSSL can respond differently to the calling application if a 0 byte record is received with invalid padding compared to if a 0 byte record is received with an invalid MAC. If the application then behaves differently based on that in a way that is detectable to the remote peer, then this amounts to a padding oracle that could be used to decrypt data. In order for this to be exploitable "non-stitched" ciphersuites must be in use. Stitched ciphersuites are optimised implementations of certain commonly used ciphersuites. Also the application must call SSL_shutdown() twice even if a protocol error has occurred (applications should not do this but some do anyway). Fixed in OpenSSL 1.0.2r (Affected 1.0.2-1.0.2q).

How to fix CVE-2019-1559

To remediate CVE-2019-1559, upgrade the affected package to a fixed version below.

—upgrade to 1.0.2r-r0 or later
—upgrade to 1.1.0b-2 or later
—upgrade to 1.0.1t-1+deb8u11 or later
—upgrade to 1.0.2r-1~deb9u1 or later

Is CVE-2019-1559 being exploited?

Low — EPSS is 5.0%, meaning exploitation activity has not been observed at scale.

Affected packages (4)

from 0, < 1.0.2r-r0
from 0, < 1.1.0b-2
from 0, < 1.0.1t-1+deb8u11
from 0, < 1.0.2r-1~deb9u1

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 3.1	MEDIUM5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N