Summary
-------
Six 0day exploits were filed against Exim.

None of these issues is related to transport security (TLS) being
on or off.

* 3 of them are related to SPA/NTLM, and EXTERNAL auth. If you do not
  use SPA/NTLM, or EXTERNAL authentication, you're not affected.  These
  issues are fixed.

* One issue is related to data received from a proxy-protocol proxy. If
  you do not use a proxy in front of Exim, you're not affected. If your
  proxy is trustworthy, you're not affected. We're working on a fix.

* One is related to libspf2. If you do not use the `spf` lookup type or
  the `spf` ACL condition, you are not affected.

* The last one is related to DNS lookups. If you use a trustworthy
  resolver (which does validation of the data it receives), you're not
  affected. We're working on a fix.

Schedule
--------
Currently we're in contact with the major distros and aim to release
those fixes that are available as soon as possible. (Aiming Monday, Oct
2nd.)


More Details
------------

ZDI-23-1468 | ZDI-CAN-17433 | CVE-2023-42114 | Exim bug 3001
------------------------------------------------------------
Subject:    NTLM Challenge Out-Of-Bounds Read
CVSS Score: 3.7
Mitigation: Do not use SPA (NTLM) authentication
Subsystem:  SPA auth
Fixed:      04107e98d, 4.96.1, 4.97

ZDI-23-1469 | ZDI-CAN-17434 | CVE-2023-42115 | Exim bug 2999
------------------------------------------------------------
Subject:    AUTH Out-Of-Bounds Write
CVSS Score: 9.8
Mitigation: Do not offer EXTERNAL authentication.
Subsystem:  EXTERNAL auth
Fixed:      7bb5bc2c6, 4.96.1, 4.97

ZDI-23-1470 | ZDI-CAN-17515 | CVE-2023-42116 | Exim bug 3000
------------------------------------------------------------
Subject:    SMTP Challenge Stack-based Buffer Overflow
CVSS Score: 8.1
Mitigation: Do not use SPA (NTLM) authentication
Subsystem:  SPA auth
Fixed:      e17b8b0f1, 4.96.1, 4.97

ZDI-23-1471 | ZDI-CAN-17554 | CVE-2023-42117 | Exim Bug 3031
-------------------------------------------------------------
Subject:    Improper Neutralization of Special Elements
CVSS Score: 8.1
Mitigation: Do not use Exim behind an untrusted proxy-protocol proxy
Subsystem:  proxy protocol (not socks!)
Fix:        not yet

ZDI-23-1472 | ZDI-CAN-17578 | CVE-2023-42118 | Exim Bug 3032
------------------------------------------------------------
Subject:    libspf2 Integer Underflow
CVSS Score: 7.5
Mitigation: Do not use the `spf` condition in your ACL
Subsystem:  spf
Remark:     It is debatable if this should be filed against
            libspf2.

ZDI-23-1473 | ZDI-CAN-17643 | CVE-2023-42219 | Exim Bug 3033
------------------------------------------------------------
Subject:    dnsdb Out-Of-Bounds Read
CVSS Score: 3.1
Mitigation: Use a trustworthy DNS resolver which is able to
            validate the data according to the DNS record types.
Subsystem:  dns lookups
Fix:        not yet
Remark:     It is still under consideration.