https://www.zerodayinitiative.com/advisories/ZDI-23-1469/
currently no fix available
EDIT:
Maybe some improvement:
https://www.openwall.com/lists/oss-security/2023/09/29/5
Ein Paar Infos dazu in Deutsch:
Some facts in german:
https://www.heise.de/news/Kritische-Luecke-im-Mailserver-Exim-9321943.html
edlin
gefixt in exim4 4.97~RC1-2
fixed in exim4 4.97~RC1-2