Date: Mon, 25 Sep 2023 12:29:11 +0200 From: Solar Designer <solar@...nwall.com> To: oss-security@...ts.openwall.com Subject: CVE-2023-4527: glibc: Stack read overflow in getaddrinfo in no-aaaa mode Hi, A bug affecting glibc 2.36+ was reported and fixed earlier this month: https://sourceware.org/bugzilla/show_bug.cgi?id=30842 > Florian Weimer 2023-09-12 15:16:27 UTC > > If the system is configured in no-aaaa mode via /etc/resolv.conf, > getaddrinfo is called for the AF_UNSPEC address family, and a DNS > response is received over TCP that is larger than 2048 bytes, > getaddrinfo may potentially disclose stack contents via the returned > address data, or crash. While name lookup normally just fails > incorrectly, crashes are not difficult to trigger, with valid DNS > responses that are propagated by DNS resolvers. > > Introduced by: > > commit f282cdbe7f436c75864e5640a409a10485e9abb2 > Author: Florian Weimer <fweimer@...hat.com> > Date: Fri Jun 24 18:16:41 2022 +0200 > > resolv: Implement no-aaaa stub resolver option > > Reviewed-by: Carlos O'Donell <carlos@...hat.com> > Florian Weimer 2023-09-13 12:58:01 UTC > > All impacted branches fixed. Even though upstream 2.35 and older are not affected, the problematic commit was backported into some distro packages of older glibc: https://access.redhat.com/security/cve/CVE-2023-4527 > Statement > This issue only affect systems configured with no-aaaa mode via > /etc/resolv.conf. > > The no-aaaa stub resolver option was backported only to Red Hat > Enterprise Linux versions 8.7 and 9.1. Therefore, previous versions are > not affected. > > Mitigation > Removing the no-aaaa diagnostic option from /etc/resolv.conf will > mitigate this flaw. Also tracked here: https://bugzilla.redhat.com/show_bug.cgi?id=2234712 The feature is described in a glibc NEWS entry for 2.36 as follows: https://lists.gnu.org/archive/html/info-gnu/2022-08/msg00000.html > * The "no-aaaa" DNS stub resolver option has been added. System > administrators can use it to suppress AAAA queries made by the stub > resolver, including AAAA lookups triggered by NSS-based interfaces > such as getaddrinfo. Only DNS lookups are affected: IPv6 data in > /etc/hosts is still used, getaddrinfo with AI_PASSIVE will still > produce IPv6 addresses, and configured IPv6 name servers are still > used. To produce correct Name Error (NXDOMAIN) results, AAAA queries > are translated to A queries. The new resolver option is intended > primarily for diagnostic purposes, to rule out that AAAA DNS queries > have adverse impact. It is incompatible with EDNS0 usage and DNSSEC > validation by applications. Alexander
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