An OpenSSL security update has been released for Ubuntu Linux 18.04 LTS and 16.04 LTS.

USN-4504-1: OpenSSL vulnerabilities

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Ubuntu Security Notice USN-4504-1
September 16, 2020

openssl, openssl1.0 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in OpenSSL.

Software Description:
- openssl1.0: Secure Socket Layer (SSL) cryptographic library and tools
- openssl: Secure Socket Layer (SSL) cryptographic library and tools

Details:

Robert Merget, Marcus Brinkmann, Nimrod Aviram, and Juraj Somorovsky
discovered that certain Diffie-Hellman ciphersuites in the TLS
specification and implemented by OpenSSL contained a flaw. A remote
attacker could possibly use this issue to eavesdrop on encrypted
communications. This was fixed in this update by removing the insecure
ciphersuites from OpenSSL. (CVE-2020-1968)

Cesar Pereida García, Sohaib ul Hassan, Nicola Tuveri, Iaroslav Gridin,
Alejandro Cabrera Aldaya, and Billy Brumley discovered that OpenSSL
incorrectly handled ECDSA signatures. An attacker could possibly use this
issue to perform a timing side-channel attack and recover private ECDSA
keys. This issue only affected Ubuntu 18.04 LTS. (CVE-2019-1547)

Guido Vranken discovered that OpenSSL incorrectly performed the x86_64
Montgomery squaring procedure. While unlikely, a remote attacker could
possibly use this issue to recover private keys. This issue only affected
Ubuntu 18.04 LTS. (CVE-2019-1551)

Bernd Edlinger discovered that OpenSSL incorrectly handled certain
decryption functions. In certain scenarios, a remote attacker could
possibly use this issue to perform a padding oracle attack and decrypt
traffic. This issue only affected Ubuntu 18.04 LTS. (CVE-2019-1563)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 18.04 LTS:
libssl1.0.0 1.0.2n-1ubuntu5.4

Ubuntu 16.04 LTS:
libssl1.0.0 1.0.2g-1ubuntu4.17

After a standard system update you need to reboot your computer to make
all the necessary changes.

References:
  https://usn.ubuntu.com/4504-1
CVE-2019-1547, CVE-2019-1551, CVE-2019-1563, CVE-2020-1968

Package Information:
  https://launchpad.net/ubuntu/+source/openssl1.0/1.0.2n-1ubuntu5.4
  https://launchpad.net/ubuntu/+source/openssl/1.0.2g-1ubuntu4.17