-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 fetchmail-SA-2005-01: security announcement Topic: remote code injection vulnerability in fetchmail Author: Matthias Andree Version: 1.02 Announced: 2005-07-21 Type: buffer overrun/stack corruption/code injection Impact: account or system compromise possible through malicious or compromised POP3 servers Danger: high: in sensitive configurations, a full system compromise is possible (for 6.2.5.1: denial of service for the whole fetchmail system is possible) CVE Name: CAN-2005-2335 URL: http://fetchmail.berlios.de/fetchmail-SA-2005-01.txt http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=212762 http://www.vuxml.org/freebsd/3497d7be-2fef-45f4-8162-9063751b573a.html http://www.vuxml.org/freebsd/3f4ac724-fa8b-11d9-afcf-0060084a00e5.html http://www.freebsd.org/cgi/query-pr.cgi?pr=83805 http://www.heise.de/security/news/meldung/62070 Thanks: Edward J. Shornock (located the bug in UIDL code) Miloslav Trmac (pointed out 6.2.5.1 was faulty) Ludwig Nussel (provided minimal correct fix) Affects: fetchmail version 6.2.5.1 (denial of service) fetchmail version 6.2.5 (code injection) fetchmail version 6.2.0 (code injection) (other versions have not been checked) Not affected: fetchmail 6.2.5.2 fetchmail 6.2.6-pre7 fetchmail 6.3.0 (not released yet) Older versions may not have THIS bug, but had been found to contain other security-relevant bugs. Corrected: 2005-07-22 01:37 UTC (SVN) - committed bugfix (r4157) 2005-07-22 fetchmail-patch-6.2.5.2 released 2005-07-23 fetchmail-6.2.5.2 tarball released 0. Release history 2005-07-20 1.00 - Initial announcement 2005-07-22 1.01 - Withdrew 6.2.5.1 and 6.2.6-pre5, the fix was buggy and susceptible to denial of service through single-byte read from 0 when either a Message-ID: header was empty (in violation of RFC-822/2822) or the UIDL response did not contain an UID (in violation of RFC-1939). - Add Credits. - Add 6.2.5.1 failure details to sections 2 and 3 - Revise section 5 and B. 2005-07-26 1.02 - Revise section 0. - Add FreeBSD VuXML URL for 6.2.5.1. - Add heise security URL. - Mention release of 6.2.5.2 tarball. 1. Background fetchmail is a software package to retrieve mail from remote POP2, POP3, IMAP, ETRN or ODMR servers and forward it to local SMTP, LMTP servers or message delivery agents. 2. Problem description The POP3 code in fetchmail-6.2.5 and older that deals with UIDs (from the UIDL) reads the responses returned by the POP3 server into fixed-size buffers allocated on the stack, without limiting the input length to the buffer size. A compromised or malicious POP3 server can thus overrun fetchmail's stack. This affects POP3 and all of its variants, for instance but not limited to APOP. In fetchmail-6.2.5.1, the attempted fix prevented code injection via POP3 UIDL, but introduced two possible NULL dereferences that can be exploited to mount a denial of service attack. 3. Impact In fetchmail-6.2.5 and older, very long UIDs can cause fetchmail to crash, or potentially make it execute code placed on the stack. In some configurations, fetchmail is run by the root user to download mail for multiple accounts. In fetchmail-6.2.5.1, a server that responds with UID lines containing only the article number but no UID (in violation of RFC-1939), or a message without Message-ID when no UIDL support is available, can crash fetchmail. 4. Workaround No reasonable workaround can be offered at this time. 5. Solution Upgrade your fetchmail package to version 6.2.5.2. You can either download a complete tarball of fetchmail-6.2.5.2.tar.gz, or you can download a patch against fetchmail-6.2.5 if you already have the 6.2.5 tarball. Either is available from: To use the patch: 1. download fetchmail-6.2.5.tar.gz (or retrieve the version you already had downloaded) and fetchmail-patch-6.2.5.2.tar.gz 2. unpack the tarball: gunzip -c fetchmail-6.2.5.tar.gz | tar xf - 3. unpack the patch: gunzip fetchmail-patch-6.2.5.2.gz 4. apply the patch: cd fetchmail-6.2.5 ; patch -p1 <../fetchmail-patch-6.2.5.2 5. now configure and build as usual - detailed instructions in the file named "INSTALL". A. References fetchmail home page: B. Copyright, License and Warranty (C) Copyright 2005 by Matthias Andree, . Some rights reserved. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs German License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/2.0/de/ or send a letter to Creative Commons; 559 Nathan Abbott Way; Stanford, California 94305; USA. THIS WORK IS PROVIDED FREE OF CHARGE AND WITHOUT ANY WARRANTIES. Use the information herein at your own risk. END OF fetchmail-SA-2005-01.txt -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (GNU/Linux) iD8DBQFC5lpIvmGDOQUufZURAlv1AKCUuwHKgC/lln+fhYgt8Ba6VxI1WQCgpmBj SLivUn3+6/zifjC4Hnaw0uc= =PebP -----END PGP SIGNATURE-----