IBM Db2 11.5.0 through 11.5.9, and 12.1.0 through 12.1.4 is vulnerable to a denial of service when executing a specially crafted query with a small statement heap.
1) Increase statement heap by setting larger STMTHEAP.
or
2) Reduce optimization level to 0. The user can append a optimizer guideline to the query:
<query>
/* <OPTGUIDELINES>
<QRYOPT VALUE='0'/>
</OPTGUIDELINES> */
Customers running any vulnerable affected level of an affected Program, V11.5, and V12.1, can download the special build containing the interim fix for this issue from Fix Central. These special builds are available based on the most recent level for each impacted release: V11.5.9, and V12.1.4. They can be applied to any affected level of the appropriate release to remediate this vulnerability.
ReleaseFixed in mod packAPARDownload URLV11.5TBD https://www.ibm.com/support/pages/node/7087189
V12.1
TBD
https://www.ibm.com/support/pages/node/7267513
IBM does not disclose key Db2 functionality nor replication steps for a vulnerability to avoid providing too much information to any potential malicious attacker. IBM does not want to enable a malicious attacker with sufficient knowledge to craft an exploit of the vulnerability.