Linux Security
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    Linux Security

    ArchLinux: 202006-13: bind: denial of service

    Date 30 Jun 2020
    297
    Posted By LinuxSecurity Advisories
    The package bind before version 9.16.4-1 is vulnerable to denial of service.
    Arch Linux Security Advisory ASA-202006-13
    ==========================================
    
    Severity: Medium
    Date    : 2020-06-28
    CVE-ID  : CVE-2020-8618 CVE-2020-8619
    Package : bind
    Type    : denial of service
    Remote  : Yes
    Link    : https://security.archlinux.org/AVG-1191
    
    Summary
    =======
    
    The package bind before version 9.16.4-1 is vulnerable to denial of
    service.
    
    Resolution
    ==========
    
    Upgrade to 9.16.4-1.
    
    # pacman -Syu "bind>=9.16.4-1"
    
    The problems have been fixed upstream in version 9.16.4.
    
    Workaround
    ==========
    
    None.
    
    Description
    ===========
    
    - CVE-2020-8618 (denial of service)
    
    An assertion check in BIND before 9.16.4 (that is meant to prevent
    going beyond the end of a buffer when processing incoming data) can be
    incorrectly triggered by a large response during zone transfer. An
    attacker who is permitted to send zone data to a server via zone
    transfer can exploit this to intentionally trigger the assertion
    failure with a specially constructed zone, denying service to clients.
    
    - CVE-2020-8619 (denial of service)
    
    An issue has been found in Bind before 9.16.4, where an asterisk
    character in an empty non-terminal can cause an assertion failure in
    rbtdb.c.
    The asterisk character ("*") is allowed in DNS zone files, where it is
    most commonly present as a wildcard at a terminal node of the Domain
    Name System graph. However, the RFCs do not require and BIND does not
    enforce that an asterisk character be present only at a terminal node.
    A problem can occur when an asterisk is present in an empty non-
    terminal location within the DNS graph. If such a node exists, after a
    series of queries, named can reach an inconsistent state that results
    in the failure of an assertion check in rbtdb.c, followed by the
    program exiting due to the assertion failure.
    Unless a nameserver is providing authoritative service for one or more
    zones and at least one zone contains an empty non-terminal entry
    containing an asterisk ("*") character, this defect cannot be
    encountered. A would-be attacker who is allowed to change zone content
    could theoretically introduce such a record in order to exploit this
    condition to cause denial of service, though we consider the use of
    this vector unlikely because any such attack would require a
    significant privilege level and be easily traceable.
    
    Impact
    ======
    
    A remote attacker with enough privileges to update a zone might be able
    to crash a server via a crafted zone transfer or by inserting an
    asterisk at a terminal node of a zone.
    
    References
    ==========
    
    https://downloads.isc.org/isc/bind9/9.16.4/doc/arm/html/notes.html#notes-for-bind-9-16-4
    https://kb.isc.org/docs/cve-2020-8618
    https://gitlab.isc.org/isc-projects/bind9/-/issues/1850
    https://kb.isc.org/docs/cve-2020-8619
    https://gitlab.isc.org/isc-projects/bind9/-/issues/1718
    https://gitlab.isc.org/isc-projects/bind9/-/commit/569cc155b8680d8ed12db1fabbe20947db24a0f9
    https://security.archlinux.org/CVE-2020-8618
    https://security.archlinux.org/CVE-2020-8619
    

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