Vulnerability Details

OpenSSL: ChaCha20-Poly1305 with long nonces (CVE-2019-1543) (Linux)

Published: 2019-07-03 06:06:21
CVE Author: NIST National Vulnerability Database

CVSS Base Vector:
AV:N/AC:M/Au:N/C:P/I:P/A:N

Summary:
This host is running OpenSSL and is prone to vulnerability which allows a nonce reuse.

Detection Method:
Checks if a vulnerable version is present on the target host.

Technical Details:
ChaCha20-Poly1305 is an AEAD cipher, and requires a unique nonce input for every encryption operation. RFC 7539 specifies that the nonce value (IV) should be 96 bits (12 bytes). OpenSSL allows a variable nonce length and front pads the nonce with 0 bytes if it is less than 12 bytes. However it also incorrectly allows a nonce to be set of up to 16 bytes. In this case only the last 12 bytes are significant and any additional leading bytes are ignored. It is a requirement of using this cipher that nonce values are unique. Messages encrypted using a reused nonce value are susceptible to serious confidentiality and integrity attacks. If an application changes the default nonce length to be longer than 12 bytes and then makes a change to the leading bytes of the nonce expecting the new value to be a new unique nonce then such an application could inadvertently encrypt messages with a reused nonce. Additionally the ignored bytes in a long nonce are not covered by the integrity guarantee of this cipher. Any application that relies on the integrity of these ignored leading bytes of a long nonce may be further affected. Any OpenSSL internal use of this cipher, including in SSL/TLS, is safe because no such use sets such a long nonce value. However user applications that use this cipher directly and set a non-default nonce length to be longer than 12 bytes may be vulnerable.

Affected Versions:
OpenSSL versions 1.1.1 up to and including 1.1.1b and 1.1.0 up to and including 1.1.0j. This issue does not impact OpenSSL 1.0.2.

Recommendations:
Upgrade OpenSSL to version 1.1.0k, 1.1.1c or later. See the references for more details.

Detection Type:
Remote Banner Unreliable

Solution Type:
Vendor Patch

NIST (National Institute of Standards and Technology) NVD (National Vulnerability Database)

https://nvd.nist.gov/vuln/detail/CVE-2019-1543

References:

https://www.openssl.org/news/secadv/20190306.txt
https://seclists.org/bugtraq/2019/Jul/3
https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=ee22257b1418438ebaf54df98af4e24f494d1809
https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=f426625b6ae9a7831010750490a5f0ad689c5ba3
https://www.openssl.org/news/cl111.txt
https://www.openssl.org/news/cl110.txt

Severity
Medium
CVSS Score
5.8
Published
2019-07-03
Modified
2019-07-03
Category
General

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