On Sun, Jun 30, 2024 at 6:13 PM Greg Wooledge <g...@wooledge.org> wrote: > > On Sun, Jun 30, 2024 at 23:08:01 +0100, Tim Woodall wrote: > > According to this > > https://support.trustwave.com/kb/KnowledgebaseArticle10016.aspx > > > > bare CRs aren't allowed in emails but this has always worked. > > > > I'm only likely to have cron generating emails like this. > > > > Strange that this would have been changed in a stable release. It > > doesn't seem to have been a security update. > > It looks like it's coming from this change: > > https://metadata.ftp-master.debian.org/changelogs//main/s/sendmail/sendmail_8.17.1.9-2+deb12u2_changelog > > * Fix CVE-2023-51765 (Closes: #1059386): > sendmail allowed SMTP smuggling in certain configurations. > Remote attackers can use a published exploitation > technique to inject e-mail messages with a spoofed > MAIL FROM address, allowing bypass of an SPF protection > mechanism. This occurs because sendmail supports > <LF>.<CR><LF> but some other popular e-mail servers > do not. This is resolved with 'o' in srv_features. > > I don't know the details of how this leads to a security hole.
Take a look at the blog at <https://sec-consult.com/blog/detail/smtp-smuggling-spoofing-e-mails-worldwide/>. Jeff
