-CVE ID: CVE-2016-9963
-Date: 2016-12-15
-Credits: Bjoern Jacke <bjoern@j3e.de>
-Version(s): 4.69 -> 4.87
-Issue: If several conditions are met, Exim leaks private information
- to a remote attacker.
-
-Conditions
-==========
-
-If *all* of the following conditions are met
-
- Build options
- -------------
-
- * Exim is built with DKIM enabled (default for newer versions)
- exim -bV | grep 'Support.*DKIM'
-
- Runtime options
- ---------------
-
- * Exim uses DKIM signing (transport options dkim_private_key,
- dkim_domain, and other)
-
- * The dkim_private_key option names a file containing the key.
-
- exim -bP transports | grep 'dkim_private_key = .'
-
- * Exim uses PRDR (transport option hosts_try_prdr) (default
- since 4.86)
-
- exim -bP transports | grep 'hosts_try_prdr = .'
-
- *OR*
-
- Exim uses the LMTP protocol variant for SMTP transport.
-
- exim -bP transports | grep 'protocol = lmtp'
-
- Operation
- ---------
-
- * Exim transports a multi-recipient message
-
- * The destination host supports PRDR
- OR
- the message transport uses LMTP
-
- * One or more recipients are rejected after the DATA phase
-
-Impact
-======
-
-Exim leaks the private DKIM signing key to the log files. Additionally,
-if the build option EXPERIMENTAL_DSN_INFO=yes is used, the key material
-is included in the bounce message.
-
-Fix
-===
-
-Install a fixed Exim version:
-
- 4.88
- 4.87.1
-
-If you can't install one of the above versions, ask your package
-maintainer for a version containing the backported fix. On request and
-depending on our resources we will support you in backporting the fix.
-(Please note, that Exim project officially doesn't support versions
-prior the current stable version.)
-
-If you think that you MIGHT be affected, we HIGHLY recommend to create
-a new set of DKIM keys and fade out the previous DKIM key soon to make
-sure that a possibly leaked DKIM key can not be misused in the future.
-
-
-Workaround
-==========
-
-Disable PRDR in your outgoing transport(s): set hosts_try_prdr to an
-empty string.
-
-AND do not use the LMTP protocol variant of the SMTP driver.
-
-Indication
-==========
-
-You can check if you where affected already. The mainlog entries look like this:
-
-2016-12-17 09:44:33 10HmaX-0005vi-00 ** baduser@test.ex R=client T=send_to_server H=ip4.ip4.ip4.ip4 [ip4.ip4.ip4.ip4]: PRDR error after -----BEGIN RSA PRIVATE KEY-----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\nfKQax6vhiMq+0qIiEwLA1wavyLVKZ7Mfag+/4NTcDUVC\n-----END RSA PRIVATE KEY-----\n: 550 PRDR R=<baduser@test.ex> refusal
-
-Even if there is no evidence in the existing log files, that a DKIM key
-leakage happened this might have happened in the past, log files might
-have been deleted already but a key leak could have ended up via mail
-bounce in a user mail box
git://git.exim.org / exim-website.git / blobdiff