OpenSSL Security Advisory

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Tue Sep 10 16:18:55 UTC 2019

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OpenSSL Security Advisory [10 September 2019]

ECDSA remote timing attack (CVE-2019-1547)

Severity: Low

Normally in OpenSSL EC groups always have a co-factor present and this is used
in side channel resistant code paths. However, in some cases, it is possible to
construct a group using explicit parameters (instead of using a named curve). In
those cases it is possible that such a group does not have the cofactor present.
This can occur even where all the parameters match a known named curve.

If such a curve is used then OpenSSL falls back to non-side channel resistant
code paths which may result in full key recovery during an ECDSA signature

In order to be vulnerable an attacker would have to have the ability to time
the creation of a large number of signatures where explicit parameters with no
co-factor present are in use by an application using libcrypto.

For the avoidance of doubt libssl is not vulnerable because explicit parameters
are never used.

OpenSSL versions 1.1.1, 1.1.0 and 1.0.2 are affected by this issue.

OpenSSL 1.1.1 users should upgrade to 1.1.1d
OpenSSL 1.1.0 users should upgrade to 1.1.0l
OpenSSL 1.0.2 users should upgrade to 1.0.2t

This issue was reported by Cesar Pereida García, Sohaib ul Hassan,
Nicola Tuveri, Iaroslav Gridin, Alejandro Cabrera Aldaya, and Billy Brumley. The
fix was developed by Billy Brumley. It was reported to OpenSSL on 5th August

Fork Protection (CVE-2019-1549)

Severity: Low

OpenSSL 1.1.1 introduced a rewritten random number generator (RNG). This was
intended to include protection in the event of a fork() system call in order to
ensure that the parent and child processes did not share the same RNG state.
However this protection was not being used in the default case.

A partial mitigation for this issue is that the output from a high precision
timer is mixed into the RNG state so the likelihood of a parent and child
process sharing state is significantly reduced.

If an application already calls OPENSSL_init_crypto() explicitly using
OPENSSL_INIT_ATFORK then this problem does not occur at all.

OpenSSL version 1.1.1 is affected by this issue.

OpenSSL 1.1.1 users should upgrade to 1.1.1d

This issue was reported by Matt Caswell. The fix was developed by Matthias
St. Pierre. It was reported to OpenSSL on 27th May 2019.

Padding Oracle in PKCS7_dataDecode and CMS_decrypt_set1_pkey (CVE-2019-1563)

Severity: Low

In situations where an attacker receives automated notification of the success
or failure of a decryption attempt an attacker, after sending a very large
number of messages to be decrypted, can recover a CMS/PKCS7 transported
encryption key or decrypt any RSA encrypted message that was encrypted with the
public RSA key, using a Bleichenbacher padding oracle attack. Applications are
not affected if they use a certificate together with the private RSA key to the
CMS_decrypt or PKCS7_decrypt functions to select the correct recipient info to

OpenSSL 1.1.1 users should upgrade to 1.1.1d
OpenSSL 1.1.0 users should upgrade to 1.1.0l
OpenSSL 1.0.2 users should upgrade to 1.0.2t

This issue was reported by and the fix developed by Bernd Edlinger. It was
reported to OpenSSL on 21st August 2019.


OpenSSL 1.0.2 is currently only receiving security updates. Support for 1.0.2
will end on 31st December 2019.

Support for 1.1.0 ends on 11th September 2019 so 1.1.0l is expected to be the
last 1.1.0 release.

Users of these versions should upgrade to OpenSSL 1.1.1.


URL for this Security Advisory:

Note: the online version of the advisory may be updated with additional details
over time.

For details of OpenSSL severity classifications please see:


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