| 1.1.1.1 |
| 20-May-2026 |
christos | Import bind 9.20.23 (previous was 9.20.22)
Security Fixes
Limit resolver server list size. (CVE-2026-3592)
When resolving a domain with many nameservers that shared overlapping
IP addresses (e.g., 10 NS records all pointing at the same set of
addresses), BIND could previously waste time querying duplicate
addresses and build up excessively large server lists. Addresses
in the resolver's server list are now deduplicated so that each
unique IP is only queried once per resolution attempt, regardless
of how many NS records point to it. The number of addresses stored
per nameserver name is also now capped at six (combined A and AAAA),
preventing memory and CPU overhead from domains with unusually
large NS/glue sets.
ISC would like to thank Shuhan Zhang from Tsinghua University for
reporting this issue. [GL #5641]
Fix GSS-API resource leak. (CVE-2026-3039)
A memory leak was fixed where each GSS-API TKEY negotiation leaked
a security context inside the GSS library. An unauthenticated
attacker could exhaust server memory by sending repeated TKEY
queries to a server with tkey-gssapi-keytab configured. The leaked
memory was allocated by the GSS library, bypassing BIND's memory
accounting.
Multi-round GSS-API negotiation (GSS_S_CONTINUE_NEEDED) is now
rejected, as BIND never supported it correctly and Kerberos/SPNEGO
completes in a single round.
ISC would like to thank Vitaly Simonovich for bringing this
vulnerability to our attention. [GL #5752]
Disable recursion, UPDATE, and NOTIFY for non-IN views. (CVE-2026-5946)
Recursion, dynamic updates (UPDATE), and zone change notifications
(NOTIFY) are now disabled for views with a class other than IN
(such as CHAOS or HESIOD); authoritative service for non-IN zones
(e.g. version.bind in class CHAOS) continues to work as before.
Servers configured with recursion yes; in a non-IN view log a
warning at startup, and named-checkconf flags the same condition.
UPDATE and NOTIFY messages that specify the meta-classes ANY or
NONE in the question section are now rejected with FORMERR.
This addresses a set of closely related security issues collectively
identified as CVE-2026-5946. ISC would like to thank Mcsky23 for
bringing these issues to our attention. [GL #5784]
Avoid unbounded recursion loop. (CVE-2026-5950)
A bug during bad server handling could cause the resolver to enter
an infinite loop, continuously sending queries to an upstream server
with no exit condition, until the resolver query timeout was hit.
This has been fixed.
ISC would like to thank Billy Baraja (BielraX) for bringing this
issue to our attention. [GL #5804]
dfmt: Command not found.
A resolver could crash when handling a SIG(0)-signed response if
the matching client query was cancelled while signature verification
was still in progress for example, when the recursive-clients
quota was exhausted. This has been fixed.
ISC would like to thank Naoki Wakamatsu for bringing this vulnerability
to our attention. [GL #5819]
Fix use-after-free error in DNS-over-HTTPS when processing HTTP/2
SETTINGS frames. (CVE-2026-3593)
Previously, a use-after-free vulnerability in the DNS-over-HTTPS
implementation could cause named to crash when a client sent a
flood of HTTP/2 SETTINGS frames while a DoH response was being
written. This affected servers with DoH (DNS-over-HTTPS) enabled
and has been fixed.
ISC would like to thank Naresh Kandula Parmar (Nottiboy) for
reporting this. [GL #5755]
Fix outgoing zone transfers' quota issue.
Unauthorized clients could consume the entire outgoing zone-transfer
quota and block authorized zone transfer clients. This has been
fixed. [GL #3589]
Feature Changes
Fix CPU spikes and slow queries when cache approaches memory limit.
Cache cleanup is now spread probabilistically to avoid CPU usage
spikes and a drop in query throughput. [GL #5891]
Bug Fixes
Use the zone file's basename as origin in DNSSEC tools.
In dnssec-signzone and dnssec-verify, when the zone origin is not
specified using the -o parameter, the default behavior is to try
to sign using the zone's file name as the origin. So, for example,
dnssec-signzone -S example.com will work, so long as the file name
matches the zone name.
This now also works if the zone is in a different directory. For
example, dnssec-signzone -S zones/example.com will set the origin
value to example.com. [GL #5678]
Fix a possible race condition during zone transfers.
The named process could terminate unexpectedly when processing an
IXFR message during a zone transfer. This has been fixed. [GL #5767]
Fix named crash when processing SIG records in dynamic updates.
Previously, named could abort if a client sent a dynamic update
containing a SIG record (the legacy signature type) to a zone
configured with an update-policy. The function dns_db_findrdataset
had an incorrect requirements prerequisite that prevented SIG
records from being looked up, which was triggered as part of
processing an UPDATE request and could be triggered remotely by
any client permitted to send updates. This has been fixed by ensuring
that SIG records are handled consistently with RRSIG records during
update processing. [GL #5818]
Fix rndc modzone behavior for a zone in named.conf.
If a zone was present in the configuration file and not originally
added by rndc addzone, rndc modzone for that zone would succeed
once but subsequent rndc modzone attempts would fail. This has been
fixed. [GL #5826]
Fix zone verification of NSEC3 signed zones.
Previously, when computing the compressed bitmap during verification
of an NSEC3-signed zone, an undersized buffer was used that resulted
in an out-of-bounds write if there were too many active windows in
the bitmap. This impacted the mirror zones which are NSEC3-signed,
dnssec-signzone and dnssec-verify. This has been fixed. [GL #5834]
Prevent a crash when using both dns64 and filter-aaaa.
An assertion failure could be triggered if both dns64 and the
filter-aaaa plugin were in use simultaneously. This happened if
the plugin triggered a second recursion process, which then attempted
to store DNS64 state information in a pointer that had already been
set by the original recursion process. This has been fixed. [GL
#5854]
Fixed an assertion failure when processing catalog zones.
If a TXT record containing an invalid name TSIG key name was found
when processing a catalog zone member's primaries definition,
dns_name_free was incorrectly called, triggering an assertion. This
has been fixed. [GL #5858]
Prevent malicious DNSSEC zones from exhausting validator CPU.
A DNSSEC-signed zone could publish a DNSKEY with an unusually large
RSA public exponent and force any validator resolving names in that
zone to spend disproportionate CPU verifying signatures. The
validator now rejects such DNSKEYs, matching the limit already
applied to keys read from files or HSMs. [GL #5881]
Fix rndc-confgen aborting on HMAC-SHA-384/512 keys above 512 bits.
rndc-confgen (with either -A hmac-sha384 or -A hmac-sha512) previously
documented a -b range of 1..1024, but any value above 512 aborted
on hardened builds instead of producing a key. The full advertised
range now works. [GL #5903]
Prevent crafted queries from degrading RRL performance.
With response rate limiting enabled, an attacker sending queries
from many spoofed source addresses could steer entries into the
same slot of the internal rate-limit table and slow down query
processing on the affected server. The table now uses a per-process
keyed hash so the placement of entries cannot be predicted or
influenced from the network. [GL #5906]
Prevent rare named crash when notifies are cancelled.
Under heavy load, named could occasionally crash when a queued
outbound notify or zone refresh was cancelled at the moment it was
being sent for example, while a zone was being reloaded or removed.
The race that caused the crash is now prevented. [GL #5915]
Stop delv from aborting on a malformed query name.
delv previously aborted with SIGABRT instead of exiting cleanly
when given a query name that failed wire-format conversion (e.g.
a label longer than 63 octets). After this change delv prints the
parse error and exits with a normal failure code. [GL #5916]
Fix a crash when reconfiguring while an NTA is being rechecked.
Previously, if named was reconfigured or shut down while a negative
trust anchor was being rechecked against authoritative servers,
the in-flight recheck could outlive the view that owned it and
cause named to crash. This has been fixed. [GL #5938]
Fix a bug in allow-query/allow-transfer catalog zone custom properties.
The named process could terminate unexpectedly when processing a
catalog zone with an invalid allow-query or allow-transfer custom
property (i.e. having a non-APL type) coexisting with the valid
property. This has been fixed. [GL #5941]
Fix a memory leak issue in catalog zones.
The named process could leak small amounts of memory when processing
a catalog zone entry which had defined custom primary servers with
TSIG keys, if both the regular primaries custom property syntax
and the legacy alternative syntax (masters) were used at the same
time. This has been fixed. [GL #5943]
Fix suppressed missing-glue check in named-checkzone.
named-checkzone and named-checkconf -z silently skipped the
missing-glue check for any NS name that had already triggered an
extra-AAAA-glue warning, so zones missing required A glue could
pass validation and be deployed with broken delegations. [GL !11899]
Implement seamless outgoing TCP connection reuse.
The resolver can and will reuse outgoing TCP connections to the
same host, as recommended by RFC 7766. This prevents a whole class
of attacks that abuse the fact that establishing a TCP connection
is expensive and it is fairly easy to deplete the outgoing TCP
ports by putting them into TIME_WAIT state.
The number of pipelined queries per connection is capped at 256 to
limit the impact of a connection drop. [GL !11845]
Reject record sets too large to serve in DNS.
When BIND was asked to store a record set whose total size exceeded
what fit in a DNS message, it would allocate memory and build the
structure, then fail later at response time. Such oversized record
sets are now rejected at the time of storage with an error, avoiding
wasted work on data that can never be served. [GL !11963]
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