Last updated 19 August 2026

Last updated 19 August 2026

If BIND encounters a particular invalid data structure in a DNS record, it will accept the invalid data, and may subsequently abort and exit.

On 22 July 2026, Internet Systems Consortium disclosed nine vulnerabilities affecting our BIND 9 software:

- CVE-2026-10723: Incorrect acceptance of NSEC3 records https://kb.isc.org/docs/cve-2026-10723 - CVE-2026-10822: Key Record using PRIVATEDNS algorithm may lead to unexpected exit https://kb.isc.org/docs/cve-2026-10822 - CVE-2026-11331: Potential wildcard CNAME RPZ policy bypass https://kb.isc.org/docs/cve-2026-11331 - CVE-2026-11605: Unnecessary validation of DNSSEC signed records https://kb.isc.org/docs/cve-2026-11605 - CVE-2026-11622: Potential memory usage beyond configured limits https://kb.isc.org/docs/cve-2026-11622 - CVE-2026-11721: Cache poisoning possible with label count discrepancy, RRSIG, and wildcards https://kb.isc.org/docs/cve-2026-11721 - CVE-2026-12617: Record ordering based unexpected exit with CNAME or DNAME https://kb.isc.org/docs/cve-2026-12617 - CVE-2026-13204: Unexpected exit in certain situations with NSEC and NSEC3 both present https://kb.isc.org/docs/cve-2026-13204 - CVE-2026-13321: DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field https://kb.isc.org/docs/cve-2026-13321

New versions of BIND 9 are available:

- https://downloads.isc.org/isc/bind9/9.20.26/ - https://downloads.isc.org/isc/bind9/9.21.24/

For more information and other release formats, consult the ISC software download page: https://www.isc.org/download/

With the public announcement of these vulnerabilities, the embargo period is ended and any updated software packages that have been prepared may be released.

-- Best regards, Michał Kępień

BIND may accept incorrect child-zone NSEC3 records as valid, allowing forged authenticated NXDOMAIN responses for sibling zones. AC:H (high complexity) keeps severity at Medium despite S:C.

BIND may accept incorrect child-zone NSEC3 records as valid, allowing forged authenticated NXDOMAIN responses for sibling zones. AC:H (high complexity) keeps severity at Medium despite S:C.

If a provably insecure domain is covered by both an NSEC and NSEC3 record at the parent, and there exist an RRSIG for only one of these types, then BIND may exit unexpectedly with an assertion while validating this proof. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

If a provably insecure domain is covered by both NSEC and NSEC3 at the parent, with an RRSIG for only one type, BIND exits with an assertion during validation.

An attacker's zone can respond with an RRSIG with fewer labels than the zone it's in, causing named to produce a wildcard name shorter than the attacker's zone — resulting in cache poisoning. Requires synth-from-dnssec yes (which IS the default).

A DNSSEC validating resolver that is under a random subdomain attack against a DNSSEC-signed zone can suffer from runaway memory usage. The attacker needs to be able to send queries faster than the resolver can perform validation. The increased memory usage can be orders of magnitude beyond the limit configured in the max-cache-size parameter. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

DNSSEC Validation Bypass via Out-of-Zone NSEC Next Field

An attacker who knows (or guesses) that a resolver uses RPZ with wildcard CNAME policies can craft query names long enough to trigger a NAMETOOLONG error condition during RPZ processing. This is not handled correctly and may lead to defeating the RPZ rule. It also may lead to an unexpected exit of the BIND 9 software.

A malicious authoritative server can send a crafted zone via the ZoneToCache function that leads to a crash of the Recursor due to insuffcient input validation.

On 5/22/26 00:31, ROI AI wrote: I understand the costs, but simply hanging all the dirty laundry out is counter productive.   Working a change in public without going into sensitive details is reasonable, but pushing vuln reports to public is careless.

[...]

As a further data point backing up this theory: We’re seeing duplicate reports of the same issue found by multiple independent groups that use LLMs, within the embargo period.

-- Jacob From: Jacob Bachmeyer <jcb62281 () gmail com> To: <oss-security () lists openwall com> Date: Thu, 21 May 2026 21:02:51 -0700 Subject: Re: [oss-security] Coordinated Disclosure in the LLM Age

On 5/21/26 01:51, ROI AI wrote: Also the entire nonsense about making the found issues public - this is absurd and just exacerbates the asymmetry problem.

By keeping the reports private, the OSS teams can deal with the issues more on their timeline.

By making them public, they add timeline pressure and enable attackers.

Why are you making it harder on yourself?  It is the opposite of what you want to do. security issues private rather seriously---and that itself has costs. any benefit when the issue was found using a tool to search for issues, due to the risk of someone else using the same tool and finding the same issue.  If that other person is another whitehat, you get a duplicate report.  If that other person is a blackhat, you get an in-the-wild exploit while you were carefully maintaining an embargo. [...]

From: ROI AI < mailto:sales () roiai ca > To: "oss-security"< mailto:oss-security () lists openwall com > Date: Wed, 20 May 2026 22:26:21 -0700 Subject: Re: [oss-security] Coordinated Disclosure in the LLM Age

People are shooting the messengers here.   The fact is - we are going through a generational security event due to the advancement of LLMs. amount of "AI" slop that has buried maintainers of major packages.  Have you forgotten already that curl had to cancel their bug bounty due to excessive "AI" slop submissions? It is also both trivial and extremely effective to use Agentic analysis to filter security reports. be incapable of precise analysis.  I understand talking your own book, but there are serious externalities here and I cannot let this go unanswered. genuine issue?  Now the issue does not get fixed... "AI" hallucinations?  Remember that the same hallucination-prone model might be doing the analysis as made the bogus report.  How, exactly, is a model supposed to recognize its own hallucinations? As for 'duplicates', people are claiming this when I have seen little evidence.  I reported a dozen or so to one major project and no one has yet claimed invalid or duplicate. manages inserting them into a bug tracker.  I am inclined to trust their experience over your hand-waving dismissal. in many projects, sent straight to the bit bucket, especially if found to be invalid.  You should not expect a response informing you that your report is invalid, as most maintainers have likely stopped bothering to send those. Moreover, if 'duplicates' are found, then that is a good signal for prioritization. issue may be "low-hanging fruit" and therefore already quasi-public.  In other words, duplicate reports could be a signal to dump the embargo and move faster to fix the issue.  (Remember that working under embargo has costs?  Those costs can extend the time to patch.) Let's stop talking about how the vulns are found and start fixing them with urgency. (< mailto:sales () roiai ca >) and realize that I am probably debating a slop machine tasked with promoting a product.  I will send this anyway, for the benefit of my fellow humans who will read this discussion and who might---just might---recognize your marketing efforts as the slop they are. ROI AI -- Jacob From: Alan Coopersmith < mailto: mailto:alan.coopersmith () oracle com > To: < mailto: mailto:oss-security () lists openwall com > Date: Wed, 20 May 2026 10:52:37 -0700 Subject: Re: [oss-security] Coordinated Disclosure in the LLM Age

On 4/28/26 07:58, Jeremy Stanley wrote: I'm sorely tempted, both due to the increased volume and the risk of premature disclosure, to just assume that any vulnerability reported as a result of research using an LLM is trivially discoverable by others, and give up trying to pretend there's any point to working it under embargo. Other maintainers under similar floods seem to agree:

Linux kernel: - https://lkml.org/lkml/2026/5/17/896 - https://docs.kernel.org/process/security-bugs.html

DNS servers (BIND, Unbound, PowerDNS): - https://indico.dns-oarc.net/event/56/contributions/1233/ - https://indico.dns-oarc.net/event/56/contributions/1233/attachments/1180/2539/presentation.pdf Confidential communication. No warranties or commitments unless in a signed agreement. If received in error, notify sender and delete. Unauthorized use prohibited.

On 4/28/26 07:58, Jeremy Stanley wrote: Other maintainers under similar floods seem to agree:

Linux kernel: - https://lkml.org/lkml/2026/5/17/896 - https://docs.kernel.org/process/security-bugs.html

DNS servers (BIND, Unbound, PowerDNS): - https://indico.dns-oarc.net/event/56/contributions/1233/ - https://indico.dns-oarc.net/event/56/contributions/1233/attachments/1180/2539/presentation.pdf

-- -Alan Coopersmith- alan.coopersmith () oracle com Oracle Solaris Engineering - https://blogs.oracle.com/solaris

An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

BIND resolvers are vulnerable to an amplified resource consumption/exhaustion attack. If a victim resolver makes a query to a specially crafted zone, the resolver will consume disproportionate resources. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Last updated 22 May 2026

Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message.

Invalid handling of CLASS != IN

Multiple flaws have been identified in named related to the handling of DNS messages whose CLASS is not Internet (IN) — for example, CHAOS or HESIOD, or DNS messages that specify meta-classes (ANY or NONE) in the question section. Specially crafted requests reaching the affected code paths — recursion, dynamic updates (UPDATE), zone change notifications (NOTIFY), or processing of IN-specific record types in non-IN data — can cause assertion failures in named.

A use-after-free vulnerability exists within the DNS-over-HTTPS implementation. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.0 through 9.18.48 and 9.18.11-S1 through 9.18.48-S1 are NOT affected.

BIND 9 server memory exhaustion during GSS-API TKEY negotiation

BIND servers that are configured to use TKEY-based authentication via GSS-API tokens are vulnerable to excessive memory consumption when receiving and processing maliciously-constructed packets. Typically these servers will be found in Active Directory integrated DNS deployments and/or Kerberos-secured DNS environments.

The BOOTP file field is written to the lease file without escaping embedded double-quotes, allowing injection of arbitrary dhclient.conf directives. When the lease file is subsequently re-parsed by dhclient, e.g., after a system restart, an attacker-controlled field from the lease is passed to dhclient-script(8), which evaluates it.

A rogue DHCP server may be able to execute arbirary code as root on a system running dhclient.

A flaw was found in dhcpcd's IPv6 Neighbor Discovery Router Advertisement processing. A specially crafted IPv6 Router Advertisement containing a zero-length Neighbor Discovery option can bypass validation during packet storage and later be reparsed without adequate validation, causing the parser to enter a non-advancing loop. Successful exploitation may result in excessive CPU consumption, leading to a denial of service.

An RPZ sent by a malicious authoritative server can result in a null pointer dereference, caused by a missing consistency check and leading to a denial of service.

In helper.c:265, the DHCPv6 CLID is hex-encoded via sprintf("%.2x") into daemon->packet (5,131 bytes) with no length cap on the CLID. DHCPv6 CLIDs can be up to 65,535 bytes (131,070 hex characters). The helper process retains root privileges. log6packet() already caps CLID to 100 bytes for logging, but the helper code path was missed. Fix: add && i < 100 bound to the encoding loop, matching the logging cap.

If a BIND resolver is performing DNSSEC validation and encounters a maliciously crafted zone, the resolver may consume excessive CPU. Authoritative-only servers are generally unaffected, although there are circumstances where authoritative servers may make recursive queries (see: https://kb.isc.org/docs/why-does-my-authoritative-server-make-recursive-queries). This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.46, 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.46-S1, and 9.20.9-S1 through 9.20.20-S1.

A specially crafted domain can be used to cause a memory leak in a BIND resolver simply by querying this domain. This issue affects BIND 9 versions 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, and 9.20.9-S1 through 9.20.20-S1. BIND 9 versions 9.18.0 through 9.18.46 and 9.18.11-S1 through 9.18.46-S1 are NOT affected.