This High severity DoS (Denial of Service) vulnerability was introduced in versions 10.1.1, 10.2.0, 10.3.24, 10.4.0, 10.5.0, 10.6.0, 10.7.1, 11.0.0, 11.1.0, 11.2.0, and 11.3.11 of Jira Service Management Data Center.

This DoS (Denial of Service) vulnerability, with a CVSS Score of 7.5 and a CVSS Vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H allows an unauthenticated attacker to expose assets in your environment susceptible to exploitation, which has no impact to confidentiality, no impact to integrity, high impact to availability, and requires no user interaction.

Atlassian recommends that Jira Service Management Data Center customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions:

• Jira Service Management Data Center 11.3: Upgrade to a release greater than or equal to 11.3.12
• Jira Service Management Data Center 10.3: Upgrade to a release greater than or equal to 10.3.26

See the release notes
(https://confluence.atlassian.com/servicemanagement/jira-service-management-release-notes-780083086.html). You can
download the latest version of Jira Service Management Data Center from the download center
(https://www.atlassian.com/software/jira/service-management/download-archives).

The National Vulnerability Database provides the following description for this vulnerability:

js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2, 4.3.2, and 5.4.1, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. In v3 & v4, merge is enabled by default so the severity score is higher. This issue is fixed in versions 3.15.2, 4.3.2, and 5.4.1.