Описание
NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.
A flaw was found in Unbound's DNSSEC validator when constructing chase-reply messages for validation. The code uses the wrong counter to calculate write offsets for ADDITIONAL section resource record sets. When a DNAME chain is combined with authority filtering, an uninitialized array slot is created that the validator later dereferences, causing an immediate process crash. Any application or infrastructure relying on Unbound for DNS resolution could be forced to exit unexpectedly, resulting in a denial-of-service condition.
Отчет
The Red Hat Product Security team has assessed the severity of this vulnerability as Important, given that it can be remotely triggered without authentication or user interaction via a single crafted DNS query. Successful exploitation allows an attacker to crash the Unbound resolver process, disrupting DNS resolution for all dependent services. The vulnerability's root cause is the use of incorrect counters to calculate write offsets, leading to dereference of an uninitialized pointer and subsequent denial-of-service.
Меры по смягчению последствий
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | unbound | Out of support scope | ||
| Red Hat Enterprise Linux 7 | unbound | Affected | ||
| Red Hat OpenShift Container Platform 4 | rhcos | Affected | ||
| Red Hat Enterprise Linux 10 | unbound | Fixed | RHSA-2026:23231 | 04.06.2026 |
| Red Hat Enterprise Linux 8 | unbound | Fixed | RHSA-2026:24365 | 08.06.2026 |
| Red Hat Enterprise Linux 9 | unbound | Fixed | RHSA-2026:24369 | 08.06.2026 |
| Red Hat Hardened Images | unbound-main-1.25.1-0.1.hum1 | Fixed | RHSA-2026:19752 | 20.05.2026 |
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Дополнительная информация
Статус:
EPSS
7.5 High
CVSS3
Связанные уязвимости
NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.
NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.
NLnet Labs Unbound up to and including version 1.25.0 has a denial of ...
EPSS
7.5 High
CVSS3