Pass "" instead of NULL to ns_client_dumpmessage() to get the log message printed.
Merge branch 'ondrej/fix-ns_client_dumpmessage-calls' into 'security-main'
See merge request isc-private/bind9!1022
A use-after-free vulnerability in the DNS-over-HTTPS implementation
could cause named to crash when a client sends a flood of HTTP/2
SETTINGS frames while a DoH response is being written. This affects
servers with DoH (DNS-over-HTTPS) enabled.
ISC would like to thank Naresh Kandula Parmar (Nottiboy) for reporting this.
For: https://gitlab.isc.org/isc-projects/bind9/-/issues/5755
Merge branch '5755-heap-user-after-free-http2-settings' into 'security-main'
See merge request isc-private/bind9!949
The two new call sites added by the CLASS-validation work passed NULL
as the reason, but ns_client_dumpmessage() bails out early on a NULL
reason — so the message dump never happened. The intent was to dump
the message and let the follow-up ns_client_log() carry the reason
text, so pass "" to suppress the prefix without short-circuiting the
dump.
Spread cache cleanup probabilistically to avoid CPU usage
spikes and a drop in query throughput.
Closesisc-projects/bind9#5891
Merge branch '5891-improve-overmem-cleaning' into 'security-main'
See merge request isc-private/bind9!1002
After the send callback completes, the UV request is freed but
the HTTP/2 socket's write buffer still points to the freed memory.
If nghttp2 subsequently needs to send frames (e.g. SETTINGS ACK),
the server_read_callback reads from the dangling buffer.
Clear the write buffer before freeing the UV request.
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 will 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.
Closes: https://gitlab.isc.org/isc-projects/bind9/-/issues/5784
Merge branch 'each-security-disable-chaos-recursion' into 'security-main'
See merge request isc-private/bind9!936
Replace the hysteretic hi_water/lo_water switch with a stochastic
check: always false below lo_water, always true at or above hi_water,
linearly ramped probability in between. This spreads cache cleaning
across many inserts instead of triggering a thundering herd once the
hi_water mark is crossed (which causes every addrdataset to enter the
LRU purge path simultaneously and serializes lookups behind the node
write locks).
The is_overmem atomic and its stores are no longer needed and are
removed. The existing tests that asserted specific hysteretic state
transitions are simplified to check only the deterministic boundaries.
Send a valid DoH query followed by a flood of SETTINGS frames to
trigger a use-after-free in the write buffer. Under ASan, named
will abort if the bug is present.
Implement RFC 3645 Section 3.1.1 client-side check for REPLAY, MUTUAL, and INTEG flags after gss_init_sec_context() completes. Add server-side INTEG flag check after gss_accept_sec_context(). Also fixes an uninitialized gss_name_t on the error path in dst_gssapi_initctx().
Merge branch 'ondrej/harden-gssapi-integration' into 'security-main'
See merge request isc-private/bind9!978
Send update messages for zones with CLASS0, ANY and NONE. The class
ANY UPDATE also attempts to delete a KX record in an existing IN
class zone to trigger a REQUIRE.
Test that the server is still running.
Fixed a memory leak 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.
Closes: https://gitlab.isc.org/isc-projects/bind9/-/issues/5752
Merge branch '5752-fix-memory-leak-in-TKEY-negotiation' into 'security-main'
See merge request isc-private/bind9!965
RFC 3645 Section 3.1.1 mandates that the client MUST abandon the
algorithm if replay_det_state is FALSE after GSS_Init_sec_context
completes. The previous commit checked MUTUAL and INTEG but missed
REPLAY, even though it was already requested in the input flags.
Add GSS_C_REPLAY_FLAG to the ret_flags bitmask check so all three
required properties (replay detection, mutual authentication, and
integrity) are verified.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Send various UPDATE requests that are known to have caused
crashes previously with deliberately misconfigured non-IN
zones; confirm that UPDATE is not processed.
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.
Closesisc-projects/bind9#5819
Merge branch '5819-fix-heap-use-after-free-in-resquery_response_continue' into 'security-main'
See merge request isc-private/bind9!964
In dst_gssapi_acceptctx(), rename outtoken to outtokenp (matching BIND
convention for output pointer parameters) and free the allocated output
token buffer on error in the cleanup path.
In process_gsstkey(), route the empty-principal error path through
cleanup via CLEANUP() instead of returning early, so that the output
token, GSS context, and TSIG key are all freed consistently by the
existing cleanup block.
After gss_accept_sec_context() completes, verify that the INTEG flag
is set in ret_flags. Without integrity protection, GSS-TSIG message
authentication cannot function correctly.
The server side was previously passing NULL for ret_flags, meaning it
never verified the negotiated security properties. The client side
was fixed in the previous commit; this fixes the server side.
When resolving a domain with many nameservers that share 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. Deduplicate addresses in the resolver's server list so that each unique IP is only queried once per resolution attempt, regardless of how many NS records point to it and cap the number of addresses stored per nameserver name to 6 (combined A and AAAA), preventing memory and CPU overhead from domains with unusually large NS/glue sets.
Closesisc-projects/bind9#5641
Merge branch '5641-selfpointedglue' into 'security-main'
See merge request isc-private/bind9!909
When a SIG(0)-signed response triggers async ECDSA verification via
dns_message_checksig_async(), the respctx_t holds a raw pointer to
the resquery_t. If the fetch context is shut down while verification
is in flight (e.g. due to recursive-clients quota exhaustion), the
query is destroyed and the callback dereferences a dangling pointer.
Take a reference on the resquery_t when initializing the respctx_t,
and release it in both cleanup paths. The query's own reference to
the fetch context keeps the fctx alive transitively.
Send crafted SPNEGO NegTokenInit tokens that propose the krb5
mechanism without a mechToken. This causes gss_accept_sec_context()
to return GSS_S_CONTINUE_NEEDED, which on unfixed code leaks the
GSS context handle (~520 bytes per query).
The test verifies that the server rejects the negotiation (TKEY
error != 0, no continuation token) rather than returning a CONTINUE
response (error=0 with output token).
After gss_init_sec_context() completes, verify that both MUTUAL and
INTEG flags are set in ret_flags. RFC 3645 Section 3.1.1 requires
the client to abandon the algorithm if either flag is missing, as
the security context would not provide mutual authentication or
message integrity.
Also fix uninitialized gss_name_t variable in dst_gssapi_initctx()
that could cause undefined behavior if gss_import_name() fails and
the cleanup path calls gss_release_name() on the uninitialized
value.
Ensure that we don't attempt an ACL match for answer addresses
when handling a class-CHAOS zone. This is an additional line of
defense for YWH-PGM40640-74.
When an upstream server answers BADCOOKIE, no matter which transport is used,
the resolver resends the query using TCP. However, if the upstream
server responded with BADCOOKIE again over TCP, the resolver would keep
resending until the maximum query count was reached.
This is now fixed by no longer resending once the query has already been
sent over TCP.
See isc-projects/bind9#5804
Merge branch '5804-resend-loop-badcookie' into 'security-main'
See merge request isc-private/bind9!988
Clarify how `max-delegation-servers` is used in the resolver, in
particular, the fact that it, in practice, caps the maximum outgoing
queries to resolve a name at a given delegation point.
Reject multi-round GSS-API negotiation (GSS_S_CONTINUE_NEEDED) in
dst_gssapi_acceptctx(). Each call to gss_accept_sec_context()
allocates a context inside the GSS library; without this fix, the
context handle was passed back to process_gsstkey() which did not
store it persistently, leaking it on every incomplete negotiation.
An unauthenticated attacker could exhaust server memory by sending
repeated TKEY queries with GSSAPI tokens, each leaking one GSS
context. The leaked memory is allocated by the GSS library via
malloc(), bypassing BIND's memory accounting.
In practice, Kerberos/SPNEGO (the only mechanism used with BIND)
completes in a single round, so rejecting continuation does not
affect real-world deployments. See RFC 3645 Section 4.1.3.
NOTIFY and UPDATE messages must specify a data class in the
QUESTION/ZONE section. NONE and ANY are meta-classes and not
appropriate here. Return FORMERR if either is used.
Rejecting messages with a query class of NONE addresses YWH-PGM40640-72,
YWH-PGM40640-82, and YWH-PGM40640-83. Rejecting messages with a query
class of ANY addresses YWH-PGM40640-87, YWH-PGM40640-88, and
YWH-PGM40640-117.
Fixes: isc-projects/bind9#5778Fixes: isc-projects/bind9#5782Fixes: isc-projects/bind9#5783Fixes: isc-projects/bind9#5797Fixes: isc-projects/bind9#5798Fixes: isc-projects/bind9#5853
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.
Closesisc-projects/bind9#5804
Merge branch '5804-resend-loop' into 'security-main'
See merge request isc-private/bind9!985
Update the resend_loop_badcookie system test to ensure there is no
attempt to resend the query using TCP when getting BADCOOKIE from an
upstream server using this transport already.
Add a new system test which ensures that the `max-delegation-servers`
limit is correctly respected also in the case a domain has only NS names
(and no glues). In particular, this test when there are multiple NS
names and multiples IPs per names.
If the number of IP (even from the first picked NS name) reaches
`max-delegation-servers`, and the resolution is not a success, the
resolver won't attempt another NS name, as it already used all its
"credit".
Reject requests with unsupported or misused CLASS values before
further processing. Only IN, CH, HS, RESERVED0 (for DNS Cookies),
ANY (for TKEY negotiation), and NONE (for DNS UPDATE) are accepted;
all other classes return NOTIMP. Misuse of NONE or ANY outside
their allowed contexts returns FORMERR.
This adds further protection against bugs of the same general class
as YWH-PGM40640-70 and YWH-PGM40640-73.
Unauthorized clients could consume outgoing zone transfers quota
and block authorized zone transfer clients. This has been fixed.
Fixesisc-projects/bind9#3589
Merge branch '3859-security-xfrout-quota-fix' into 'security-main'
See merge request isc-private/bind9!971
Calls to `rctx_resend()` are done internally within the resolver, in
flow which are not supposed to happens more than once. For instance,
if some query fails, and a specific flag "F" wasn't set, then set the
flag and try again. This wouldn't occur more than once because if the
query fails the next attempt, the flag "F" would be set already, so the
resolver would move to the next server (or give up).
However, a subtle bug missing checking a flag, for instance, could lead
to an unbounded loop re-trying to query the same server. This is now
impossible as `rctx_resend()` also increment the query counters (so if
such case occurs, it would stop once the maximum limit is reached).
The dns_resstatscounter_retry are also only incremented if the
`fctx_query()` succeeds, similar to as is done in `fctx_try()`.
When an upstream server answers BADCOOKIE, no matter the transport used,
the resolver eventually resends the query using TCP. However, if the
upstream server responds with BADCOOKIE again over TCP, the resolver
would keep resending until the maximum query count is reached.
This is now fixed by stopping resending once the query has already been
sent over TCP.
Verify that the resolver selects authoritative servers in increasing
SRTT order. Four servers are configured with increasing response
delays. 100 queries are sent, expecting most to go to the fastest
server (ns2). Then ns2 stops responding, another 100 queries are
sent and should go to ns3 (the next fastest), and so on through
ns4 and ns5. Each query uses a unique name to avoid cache hits.
Return NOTIMP for UPDATE and NOTIFY requests received for views with a
class other than IN. Only QUERY is now supported for non-IN views such
as CHAOS.
When running dns dns_rdata_tostruct() with types that are only defined
for class IN, ensure that the class is correct before proceeding.
Add an assertion that any zone being updated is of class IN. (Note
that previously, a DLZ zone could have its class value set incorrectly
to NONE; this has been fixed.)
This addresses YWH-PGM40640-70 and YWH-PGM40640-73 (as well as any
similar problems that might have occurred in the future) by minimizing
the code paths that can be reached by rdata classes other than IN, so it
is safe for the implementation to assume that rdatatypes that are only
defined for class IN, such as SVCB or WKS, have been parsed and
validated, and not accepted as unknown/opaque data.
Fixes: isc-projects/bind9#5777Fixes: isc-projects/bind9#5779
Test the resolver's behavior with self-pointed glue where each NS
has the same set of addresses. Verify that addresses are
deduplicated and each unique IP is only queried once.
Also test the NS processing limit (max-delegation-servers) and the
ADB address limit (adbaddrslimit), both individually and combined.
Force recursion off, and set allow-recursion/allow-recursion-on ACLs
to none, for views with a class other than IN. Log a configuration
warning if recursion is explicitly enabled for a non-IN view.
This addresses YWH-PGM40640-74 and YWH-PGM40640-75 by preventing any
attempt at recursive processing in a class-CHAOS view, ensuring that
server addresses used for recursive queries and received in recursive
responses are of the expected format.
Fixes: isc-projects/bind9#5780Fixes: isc-projects/bind9#5781
Run malicious server: resend_loop/ans3/ans.py
Start BIND: ns4
Send single query to test.example
The resolver will repeatedly resend queries until the fetch timeout
expires, resulting in resulting in thousands of qrysent while the quota
counter remains 0.
The SLIST (essentially `fctx->finds`, forwarders and dual-stack
alternatives aside) can have duplicate server addresses when multiple
in-domain nameservers share the same IP addresses:
sub.example. NS ns1.sub.example.
sub.example. NS ns2.sub.example.
ns1.sub.example. A 1.2.3.4
ns1.sub.example. A 5.6.7.8
ns2.sub.example. A 1.2.3.4
ns2.sub.example. A 5.6.7.8
If both 1.2.3.4 and 5.6.7.8 fail to return a valid answer, the resolver
would query each address twice.
The problem is fixed by replacing the two-phase server selection (sort
each find list by SRTT, sort finds by head SRTT) with a single linear
scan in nextaddress() that finds the lowest-SRTT unmarked, non-duplicate
address across all find lists.
The old approach had a correctness bug: after sorting, the resolver
picked the next address from the "current" find list rather than
globally. For example, with find lists [1, 15, 26] and [3, 4, 5], the
second pick would be SRTT 15 instead of the correct SRTT 3.
The new approach is both simpler and correct: each call to nextaddress()
walks all addresses, skips marked and duplicate entries, and returns the
one with the lowest SRTT. While this walk is repeated for each server
attempt, it operates on a small bounded list and is negligible compared
to the network I/O of querying the server.
The number of `dns_adbaddrfind_t` (NS address with metadata like SRTT)
returned from an ADB NS name lookup is now limited by the caller. The
default value (outside the resolver) uses `max-delegation-servers`, and
the resolver, for a given fetch, start with `max-delegation-servers` and
decrement it at each ADB fetch. This ensures that, for a given
delegation, no more than 13 nameservers will be contacted.
This is the same mechanism used when looking up `dns_adbaddrfind_t` from
a list of glues (addresses).
When a validator is being shut down, the associated name
`val->name` is set to NULL. This could cause a crash if a worker
thread subsequently added an EDE code with `val->name` in the
extra text.
`validator_addede()` now checks whether the name is NULL before
trying to add it to the extra text.
Closes#5613
Merge branch 'each-validator-log-after-shutdown' into 'main'
See merge request isc-projects/bind9!11945
When a validator is being shut down, the associated name
`val->name` is set to NULL. This could cause a crash if a worker
thread subsequently added an EDE code to the response containing
val->name in the extra text.
`validator_addede()` now checks whether the name is NULL before
trying to add it to the extra text.
The :iscman:`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.
Closes#5941
Merge branch '5941-catz-catz_process_apl-bug-fix' into 'main'
See merge request isc-projects/bind9!11954
The allow-transfer/allow-query catalog zone custom properties support
only APL RRtypes. All other types are correctly rejected by the
catz_process_apl() function. However, when an APL RRtype is processed
by that function, and another (non-APL) RRtype is then attempted to be
processed, there is an assertion failure happening in the prologue
of the function because `*aclbp != NULL` (i.e. an APL has been already
processed). Move the code to do type checking before the affected
REQUIRE assertion.
