We extended one of the most popular features of the Anchore Navigator, tag notifications, in our latest Previously users could subscribe to a tag and receive a notification when a new image was pushed with that tag. For example, if you used the Debian image as the base image for your containers then you could subscribe to receive a notification when a new release was pushed.

In addition to tag update notifications, the Navigator can now send notifications when we detect changes to the policy status of your image, for example, if your image is now failing its policy check, or when CVEs change on your image.

Seeing a CVE change notification is common but usually, you expect to see “CVE Added” however this email is different.

Here you can see that I subscribed to library/python:latest and the current image ID that’s tagged with that tag is 968120d8…. and in the body of the notification you can see that one medium severity CVE has been removed.

When the Anchore Navigator first analyzed image ID 968120d8… a list of packages was retrieved. The Anchore service regularly pulls down vulnerability data from sources such as operating system distributors and the National Vulnerability Database (NVD). We match this data against the package manifest to identify vulnerabilities in the image.

The most common change we see is when a new vulnerability is reported against a specific package. The actual workflows we see vary from distribution to distribution. It is common to see a vulnerability of unknown severity added to an image when the vulnerability is first been disclosed then once the vulnerability has been triaged it moves from unknown severity to a specific severity such as Critical, High, Medium, Low or Negligible.

In some cases as more in-depth analysis occurs a distributor or the upstream vulnerability database provider may change their assessment of not just the severity but also the version number of the vulnerable package. For example, if may initially be thought that version 2.x of package foo is vulnerable to a CVE but on further analysis, it may be found that only version 2.1 is vulnerable.
In this example, the vulnerability was analyzed and it was found that the current version of ImageMagick (version 8: in Debian Jessie is not vulnerable to this issue and so the associated feed was updated by the Debian security team. Anchore picked up the change to this feed which triggered the notifications.

Sadly seeing vulnerabilities being removed from an image is not very common, you are more likely to see new vulnerabilities being added to images or vulnerability severities being increased which is why it’s important not just to check the image once but keep a constant eye on the status of the image which is where the Anchore Navigator’s notifications feature can help.