CVE-2026-42923

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.

Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.

Security Fix(es):

NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)

NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…

Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.

Security Fix(es):

NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)

NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…

Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.

Security Fix(es):

NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)

NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…

Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn't make custom builds or provide specific features to paying customers only.

Security Fix(es):

NLnet Labs Unbound 1.6.2 up to and including version 1.25.0 has a denial of service vulnerability when compiled with DNSCrypt support ('--enable-dnscrypt'). A bad DNSCrypt query could underflow Unbound's DNSCrypt packet reading procedure that may lead to heap overflow. A malicious actor can exploit the vulnerability with a single bad DNSCrypt query that its decrypted plaintext consists entirely of '0x00' bytes and does not contain the expected '0x80' marker. Unbound would then start reading more bytes than necessary until it finds a non-'0x00' byte. Based on the underlying memory allocator and the memory layout, it could lead to heap overflow while reading followed by a crash. Likelihood of a crash is low, since it relies heavily on the underlying memory allocator and the memory layout. If the heap overflow does not happen, Unbound's later packet checks will deny the packet. Unbound 1.25.1 contains a patch with a fix to bound reading in the given buffer space.(CVE-2026-32792)

NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.(CVE-2026-40622)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the jostle logic that could defeat its purpose and degrade resolution performance. Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended.(CVE-2026-42534)

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code…

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.

• CVE-2026-42923: cap NSEC3 hash calculations in the negative-cache DS proof and reject oversized NSEC3 salt
• CVE-2024-43168: reject negative port numbers in outgoing-port-permit/avoid to prevent an out-of-bounds write

• CVE-2026-50243: do not let response-ip/rpz rewrite a BOGUS answer; return SERVFAIL
• CVE-2026-42923: cap NSEC3 hash calculations in the negative-cache DS proof and reject oversized NSEC3 salt
• CVE-2024-43168: reject negative port numbers in outgoing-port-permit/avoid to prevent an out-of-bounds write

• CVE-2026-50243: do not let response-ip/rpz rewrite a BOGUS answer; return SERVFAIL
• CVE-2026-42923: cap NSEC3 hash calculations in the negative-cache DS proof and reject oversized NSEC3 salt
• CVE-2024-43168: reject negative port numbers in outgoing-port-permit/avoid to prevent an out-of-bounds write

These are all security issues fixed in the libunbound8-1.25.1-1.1 package on the GA media of openSUSE Tumbleweed.

This update for unbound fixes the following issues

• CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
• CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
• CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
• CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
• CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
• CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
• CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
• CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
• CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
• CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
• CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).

This update for unbound fixes the following issues

• CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
• CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
• CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
• CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
• CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
• CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
• CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
• CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
• CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
• CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
• CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).

This update for unbound fixes the following issues

• CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
• CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
• CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
• CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
• CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
• CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
• CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
• CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
• CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
• CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
• CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).

This update for unbound fixes the following issues

• CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
• CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
• CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
• CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
• CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
• CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
• CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
• CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
• CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
• CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
• CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).

This update for unbound fixes the following issues

• CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
• CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
• CVE-2026-40622: "Ghost domain name" variant (bsc#1265581).
• CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
• CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
• CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
• CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
• CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
• CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
• CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
• CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).

This update for unbound fixes the following issues

• CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
• CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
• CVE-2026-40622: 'Ghost domain name' variant (bsc#1265581).
• CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
• CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
• CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
• CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
• CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
• CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
• CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
• CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).

This update for unbound fixes the following issues

• CVE-2026-32792: Packet of death with DNSCrypt (bsc#1265583).
• CVE-2026-33278: Possible remote code execution during DNSSEC validation (bsc#1265587).
• CVE-2026-40622: 'Ghost domain name' variant (bsc#1265581).
• CVE-2026-41292: Parsing a long list of incoming EDNS options degrades performance (bsc#1265580).
• CVE-2026-42534: Jostle logic bypass degrades resolution performance (bsc#1265585).
• CVE-2026-42923: Degradation of service with unbounded NSEC3 hash calculations (bsc#1265589).
• CVE-2026-42944: Heap overflow and crash with multiple nsid, cookie, padding EDNS options (bsc#1265578).
• CVE-2026-42959: Crash during DNSSEC validation of malicious content (bsc#1265586).
• CVE-2026-42960: Possible cache poisoning attack while following delegation (bsc#1265588).
• CVE-2026-44390: Unbounded name compression in certain cases causes degradation of service (bsc#1265584).
• CVE-2026-44608: Use after free and crash in RPZ code (bsc#1265582).