Detections
Analytics
Amazon Linux AMI : chrony (ALAS-2015-539)
medium Nessus Plugin ID 83978
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Synopsis
The remote Amazon Linux AMI host is missing a security update.Description
As reported upstream :When NTP or cmdmon access was configured (from chrony.conf or via authenticated cmdmon) with a subnet size that is indivisible by 4 and an address that has nonzero bits in the 4-bit subnet remainder (e.g.
192.168.15.0/22 or f000::/3), the new setting was written to an incorrect location, possibly outside the allocated array. An attacker that has the command key and is allowed to access cmdmon (only localhost is allowed by default) could exploit this to crash chronyd or possibly execute arbitrary code with the privileges of the chronyd process. (CVE-2015-1821)
When allocating memory to save unacknowledged replies to authenticated command requests, the last 'next' pointer was not initialized to NULL.
When all allocated reply slots were used, the next reply could be written to an invalid memory instead of allocating a new slot for it.
An attacker that has the command key and is allowed to access cmdmon (only localhost is allowed by default) could exploit this to crash chronyd or possibly execute arbitrary code with the privileges of the chronyd process. (CVE-2015-1822)
An attacker knowing that NTP hosts A and B are peering with each other (symmetric association) can send a packet with random timestamps to host A with source address of B which will set the NTP state variables on A to the values sent by the attacker. Host A will then send on its next poll to B a packet with originate timestamp that doesn't match the transmit timestamp of B and the packet will be dropped. If the attacker does this periodically for both hosts, they won't be able to synchronize to each other. Authentication using a symmetric key can fully protect against this attack, but in implementations following the NTPv3 (RFC 1305) or NTPv4 (RFC 5905) specification the state variables were updated even when the authentication check failed and the association was not protected. (CVE-2015-1853)
Solution
Run 'yum update chrony' to update your system.See Also
Plugin Details
Severity: Medium
ID: 83978
File Name: ala_ALAS-2015-539.nasl
Version: 2.4
Type: local
Agent: unix
Published: 6/4/2015
Updated: 12/18/2019
Supported Sensors: Agentless Assessment, Continuous Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Nessus Agent, Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 5.9
CVSS v2
Risk Factor: Medium
Base Score: 6.5
Vector: CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:P
CVSS v3
Risk Factor: Medium
Base Score: 6.5
Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Vulnerability Information
CPE: cpe:/o:amazon:linux, p-cpe:/a:amazon:linux:chrony-debuginfo, p-cpe:/a:amazon:linux:chrony
Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list
Patch Publication Date: 6/2/2015
Vulnerability Publication Date: 4/16/2015
Reference Information
CVE: CVE-2015-1821, CVE-2015-1822, CVE-2015-1853
ALAS: 2015-539