oss-security - CVE-2019-7524: Buffer overflow when reading extension header from dovecot index files

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Date: Thu, 28 Mar 2019 13:42:13 +0200
From: Aki Tuomi <aki.tuomi@...ecot.fi>
To: oss-security@...ts.openwall.com
Subject: CVE-2019-7524: Buffer overflow when reading extension header from
 dovecot index files

Dear subscribers,

we're sharing our latest advisory with you and would like to thank
everyone who contributed in finding and solving those vulnerabilities.
Feel free to join our bug bounty programs (open-xchange, dovecot,
powerdns) at HackerOne. Please find patches for v2.2.36 and v2.3.5 attached,
or download new version.

Yours sincerely,
Aki Tuomi
Open-Xchange Oy

Product: Dovecot

Vendor: OX Software GmbH

Internal reference: DOV-2964 (Bug ID)
Vulnerability type: CWE-120
Vulnerable version: 2.0.14 - 2.3.5
Vulnerable component: fts, pop3-uidl-plugin
Report confidence: Confirmed
Researcher credits: Found in internal testing
Solution status: Fixed by Vendor
Fixed version: 2.3.5.1, 2.2.36.3
Vendor notification: 2019-02-05
Solution date: 2019-03-21
Public disclosure: 2019-03-28
CVE reference: CVE-2019-7524
CVSS: 3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C (8.8)

Vulnerability Details:
When reading FTS or POP3-UIDL header from dovecot index, the input
buffer size is not bound, and data is copied to target structure causing
stack overflow.

Risk:
This can be used for local root privilege escalation or executing
arbitrary code in dovecot process context. This requires ability to
directly modify dovecot indexes.
Steps to reproduce:
Produce dovecot.index.log entry that creates an FTS header which has
more than 12 bytes of data.
Trigger dovecot indexer-worker or run doveadm index.
Dovecot will crash.

Mitigations:
Since 2.3.0 dovecot has been compiled with stack smash protection, ASLR,
read-only GOT tables and other techniques that make exploiting this bug
much harder.

Solution:
Operators should update to the latest Patch Release. The only workaround
is to disable FTS and pop3-uidl plugin.

Please find attached patches for 2.2.36 and 2.3.5.

Download attachment "dovecot-2.3.5-cve-2019-7524.tgz" of type "application/x-compressed-tar" (988 bytes)

Download attachment "dovecot-2.2.36-cve-2019-7524.tgz" of type "application/x-compressed-tar" (989 bytes)

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)

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