Isc Bind 8

Certain DNSSEC aspects of the DNS protocol (in RFC 4033, 4034, 4035, 6840, and related RFCs) allow remote attackers to cause a denial of service (CPU consumption) via one or more DNSSEC responses, aka the "KeyTrap" issue. One of the concerns is that, when there is a zone with many DNSKEY and RRSIG records, the protocol specification implies that an algorithm must evaluate all combinations of DNSKEY and RRSIG records.

To keep its cache database efficient, `named` running as a recursive resolver occasionally attempts to clean up the database. It uses several methods, including some that are asynchronous: a small chunk of memory pointing to the cache element that can be cleaned up is first allocated and then queued for later processing. It was discovered that if the resolver is continuously processing query patterns triggering this type of cache-database maintenance, `named` may not be able to handle the cleanup events in a timely manner. This in turn enables the list of queued cleanup events to grow infinitely large over time, allowing the configured `max-cache-size` limit to be significantly exceeded. This issue affects BIND 9 versions 9.16.0 through 9.16.45 and 9.16.8-S1 through 9.16.45-S1.

A bad interaction between DNS64 and serve-stale may cause `named` to crash with an assertion failure during recursive resolution, when both of these features are enabled. This issue affects BIND 9 versions 9.16.12 through 9.16.45, 9.18.0 through 9.18.21, 9.19.0 through 9.19.19, 9.16.12-S1 through 9.16.45-S1, and 9.18.11-S1 through 9.18.21-S1.

A flaw in query-handling code can cause `named` to exit prematurely with an assertion failure when:

- `nxdomain-redirect ;` is configured, and
- the resolver receives a PTR query for an RFC 1918 address that would normally result in an authoritative NXDOMAIN response. This issue affects BIND 9 versions 9.12.0 through 9.16.45, 9.18.0 through 9.18.21, 9.19.0 through 9.19.19, 9.16.8-S1 through 9.16.45-S1, and 9.18.11-S1 through 9.18.21-S1.

The DNS message parsing code in `named` includes a section whose computational complexity is overly high. It does not cause problems for typical DNS traffic, but crafted queries and responses may cause excessive CPU load on the affected `named` instance by exploiting this flaw. This issue affects both authoritative servers and recursive resolvers. This issue affects BIND 9 versions 9.0.0 through 9.16.45, 9.18.0 through 9.18.21, 9.19.0 through 9.19.19, 9.9.3-S1 through 9.11.37-S1, 9.16.8-S1 through 9.16.45-S1, and 9.18.11-S1 through 9.18.21-S1.

A flaw in the networking code handling DNS-over-TLS queries may cause `named` to terminate unexpectedly due to an assertion failure. This happens when internal data structures are incorrectly reused under significant DNS-over-TLS query load. This issue affects BIND 9 versions 9.18.0 through 9.18.18 and 9.18.11-S1 through 9.18.18-S1.

The code that processes control channel messages sent to `named` calls certain functions recursively during packet parsing. Recursion depth is only limited by the maximum accepted packet size; depending on the environment, this may cause the packet-parsing code to run out of available stack memory, causing `named` to terminate unexpectedly. Since each incoming control channel message is fully parsed before its contents are authenticated, exploiting this flaw does not require the attacker to hold a valid RNDC key; only network access to the control channel's configured TCP port is necessary. This issue affects BIND 9 versions 9.2.0 through 9.16.43, 9.18.0 through 9.18.18, 9.19.0 through 9.19.16, 9.9.3-S1 through 9.16.43-S1, and 9.18.0-S1 through 9.18.18-S1.

If the `recursive-clients` quota is reached on a BIND 9 resolver configured with both `stale-answer-enable yes;` and `stale-answer-client-timeout 0;`, a sequence of serve-stale-related lookups could cause `named` to loop and terminate unexpectedly due to a stack overflow. This issue affects BIND 9 versions 9.16.33 through 9.16.41, 9.18.7 through 9.18.15, 9.16.33-S1 through 9.16.41-S1, and 9.18.11-S1 through 9.18.15-S1.

A `named` instance configured to run as a DNSSEC-validating recursive resolver with the Aggressive Use of DNSSEC-Validated Cache (RFC 8198) option (`synth-from-dnssec`) enabled can be remotely terminated using a zone with a malformed NSEC record. This issue affects BIND 9 versions 9.16.8-S1 through 9.16.41-S1 and 9.18.11-S1 through 9.18.15-S1.

Every `named` instance configured to run as a recursive resolver maintains a cache database holding the responses to the queries it has recently sent to authoritative servers. The size limit for that cache database can be configured using the `max-cache-size` statement in the configuration file; it defaults to 90% of the total amount of memory available on the host. When the size of the cache reaches 7/8 of the configured limit, a cache-cleaning algorithm starts to remove expired and/or least-recently used RRsets from the cache, to keep memory use below the configured limit.

It has been discovered that the effectiveness of the cache-cleaning algorithm used in `named` can be severely diminished by querying the resolver for specific RRsets in a certain order, effectively allowing the configured `max-cache-size` limit to be significantly exceeded. This issue affects BIND 9 versions 9.11.0 through 9.16.41, 9.18.0 through 9.18.15, 9.19.0 through 9.19.13, 9.11.3-S1 through 9.16.41-S1, and 9.18.11-S1 through 9.18.15-S1.

This issue can affect BIND 9 resolvers with `stale-answer-enable yes;` that also make use of the option `stale-answer-client-timeout`, configured with a value greater than zero.

If the resolver receives many queries that require recursion, there will be a corresponding increase in the number of clients that are waiting for recursion to complete. If there are sufficient clients already waiting when a new client query is received so that it is necessary to SERVFAIL the longest waiting client (see BIND 9 ARM `recursive-clients` limit and soft quota), then it is possible for a race to occur between providing a stale answer to this older client and sending an early timeout SERVFAIL, which may cause an assertion failure. This issue affects BIND 9 versions 9.16.12 through 9.16.36, 9.18.0 through 9.18.10, 9.19.0 through 9.19.8, and 9.16.12-S1 through 9.16.36-S1.

BIND 9 resolver can crash when stale cache and stale answers are enabled, option `stale-answer-client-timeout` is set to a positive integer, and the resolver receives an RRSIG query. This issue affects BIND 9 versions 9.16.12 through 9.16.36, 9.18.0 through 9.18.10, 9.19.0 through 9.19.8, and 9.16.12-S1 through 9.16.36-S1.

Sending a flood of dynamic DNS updates may cause `named` to allocate large amounts of memory. This, in turn, may cause `named` to exit due to a lack of free memory. We are not aware of any cases where this has been exploited.

Memory is allocated prior to the checking of access permissions (ACLs) and is retained during the processing of a dynamic update from a client whose access credentials are accepted. Memory allocated to clients that are not permitted to send updates is released immediately upon rejection. The scope of this vulnerability is limited therefore to trusted clients who are permitted to make dynamic zone changes.

If a dynamic update is REFUSED, memory will be released again very quickly. Therefore it is only likely to be possible to degrade or stop `named` by sending a flood of unaccepted dynamic updates comparable in magnitude to a query flood intended to achieve the same detrimental outcome.

BIND 9.11 and earlier branches are also affected, but through exhaustion of internal resources rather than memory constraints. This may reduce performance but should not be a significant problem for most servers. Therefore we don't intend to address this for BIND versions prior to BIND 9.16. This issue affects BIND 9 versions 9.16.0 through 9.16.36, 9.18.0 through 9.18.10, 9.19.0 through 9.19.8, and 9.16.8-S1 through 9.16.36-S1.

By spoofing the target resolver with responses that have a malformed EdDSA signature, an attacker can trigger a small memory leak. It is possible to gradually erode available memory to the point where named crashes for lack of resources.

By spoofing the target resolver with responses that have a malformed ECDSA signature, an attacker can trigger a small memory leak. It is possible to gradually erode available memory to the point where named crashes for lack of resources.

By sending specific queries to the resolver, an attacker can cause named to crash.

An attacker can leverage this flaw to gradually erode available memory to the point where named crashes for lack of resources. Upon restart the attacker would have to begin again, but nevertheless there is the potential to deny service.

The underlying bug might cause read past end of the buffer and either read memory it should not read, or crash the process.

By flooding the target resolver with queries exploiting this flaw an attacker can significantly impair the resolver's performance, effectively denying legitimate clients access to the DNS resolution service.

On vulnerable configurations, the named daemon may, in some circumstances, terminate with an assertion failure. Vulnerable configurations are those that include a reference to http within the listen-on statements in their named.conf. TLS is used by both DNS over TLS (DoT) and DNS over HTTPS (DoH), but configurations using DoT alone are unaffected. Affects BIND 9.18.0 -> 9.18.2 and version 9.19.0 of the BIND 9.19 development branch.

BIND 9.16.11 -> 9.16.26, 9.17.0 -> 9.18.0 and versions 9.16.11-S1 -> 9.16.26-S1 of the BIND Supported Preview Edition. Specifically crafted TCP streams can cause connections to BIND to remain in CLOSE_WAIT status for an indefinite period of time, even after the client has terminated the connection.

BIND 9.11.0 -> 9.11.36 9.12.0 -> 9.16.26 9.17.0 -> 9.18.0 BIND Supported Preview Editions: 9.11.4-S1 -> 9.11.36-S1 9.16.8-S1 -> 9.16.26-S1 Versions of BIND 9 earlier than those shown - back to 9.1.0, including Supported Preview Editions - are also believed to be affected but have not been tested as they are EOL. The cache could become poisoned with incorrect records leading to queries being made to the wrong servers, which might also result in false information being returned to clients.

In BIND 9.3.0 -> 9.11.35, 9.12.0 -> 9.16.21, and versions 9.9.3-S1 -> 9.11.35-S1 and 9.16.8-S1 -> 9.16.21-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.18 of the BIND 9.17 development branch, exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.

In BIND 9.5.0 -> 9.11.29, 9.12.0 -> 9.16.13, and versions BIND 9.11.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.1 of the BIND 9.17 development branch, BIND servers are vulnerable if they are running an affected version and are configured to use GSS-TSIG features. In a configuration which uses BIND's default settings the vulnerable code path is not exposed, but a server can be rendered vulnerable by explicitly setting values for the tkey-gssapi-keytab or tkey-gssapi-credential configuration options. Although the default configuration is not vulnerable, GSS-TSIG is frequently used in networks where BIND is integrated with Samba, as well as in mixed-server environments that combine BIND servers with Active Directory domain controllers. For servers that meet these conditions, the ISC SPNEGO implementation is vulnerable to various attacks, depending on the CPU architecture for which BIND was built: For named binaries compiled for 64-bit platforms, this flaw can be used to trigger a buffer over-read, leading to a server crash. For named binaries compiled for 32-bit platforms, this flaw can be used to trigger a server crash due to a buffer overflow and possibly also to achieve remote code execution. We have determined that standard SPNEGO implementations are available in the MIT and Heimdal Kerberos libraries, which support a broad range of operating systems, rendering the ISC implementation unnecessary and obsolete. Therefore, to reduce the attack surface for BIND users, we will be removing the ISC SPNEGO implementation in the April releases of BIND 9.11 and 9.16 (it had already been dropped from BIND 9.17). We would not normally remove something from a stable ESV (Extended Support Version) of BIND, but since system libraries can replace the ISC SPNEGO implementation, we have made an exception in this case for reasons of stability and security.

In BIND 9.0.0 -> 9.11.29, 9.12.0 -> 9.16.13, and versions BIND 9.9.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.11 of the BIND 9.17 development branch, when a vulnerable version of named receives a query for a record triggering the flaw described above, the named process will terminate due to a failed assertion check. The vulnerability affects all currently maintained BIND 9 branches (9.11, 9.11-S, 9.16, 9.16-S, 9.17) as well as all other versions of BIND 9.