RHSA-2026:43588
Vulnerability from csaf_redhat - Published: 2026-07-22 14:15 - Updated: 2026-07-24 17:17Summary
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Severity
Important
Notes
Topic: An update for Red Hat Hardened Images RPMs is now available.
Details: This update includes the following RPMs:
unbound:
* python3-unbound-1.25.2-0.1.hum1 (aarch64, x86_64)
* unbound-1.25.2-0.1.hum1 (aarch64, x86_64)
* unbound-anchor-1.25.2-0.1.hum1 (aarch64, x86_64)
* unbound-devel-1.25.2-0.1.hum1 (aarch64, x86_64)
* unbound-dracut-1.25.2-0.1.hum1 (aarch64, x86_64)
* unbound-libs-1.25.2-0.1.hum1 (aarch64, x86_64)
* unbound-munin-1.25.2-0.1.hum1 (noarch)
* unbound-utils-1.25.2-0.1.hum1 (aarch64, x86_64)
* unbound-1.25.2-0.1.hum1.src (src)
Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.
A flaw was found in Unbound. Under heavy DNS-over-QUIC (DoQ) traffic, a timing discrepancy in Unbound’s libngtcp2 library can trigger an assertion failure. This causes the server to crash unexpectedly, resulting in a denial of service (DoS).
5.9 (Medium)
Affected products
Fixed
4 products
| Product | Identifier | Version | Remediation |
|---|---|---|---|
| Unresolved product id: Red Hat Hardened Images:unbound-main@aarch64 | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@noarch | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@src | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@x86_64 | — |
Vendor Fix
fix
Workaround
|
Threats
Impact
Moderate
A flaw was found in Unbound, a domain name system (DNS) resolver. When Unbound is configured with DNSCrypt support, a remote attacker could send a specially crafted DNSCrypt query over TCP. This malicious query could cause a memory error, leading to a server crash and a Denial of Service (DoS). This means legitimate users would be unable to access services relying on the Unbound server.
7.5 (High)
Affected products
Fixed
4 products
| Product | Identifier | Version | Remediation |
|---|---|---|---|
| Unresolved product id: Red Hat Hardened Images:unbound-main@aarch64 | — |
Vendor Fix
fix
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@noarch | — |
Vendor Fix
fix
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@src | — |
Vendor Fix
fix
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@x86_64 | — |
Vendor Fix
fix
|
Threats
Impact
Important
A vulnerability in Unbound allows remote attackers using malicious DNSSEC-signed servers to send malformed records that trigger a heap buffer overflow. This can cause a denial of service or potential limited information disclosure.
4.8 (Medium)
Affected products
Fixed
4 products
| Product | Identifier | Version | Remediation |
|---|---|---|---|
| Unresolved product id: Red Hat Hardened Images:unbound-main@aarch64 | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@noarch | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@src | — |
Vendor Fix
fix
Workaround
|
|
| Unresolved product id: Red Hat Hardened Images:unbound-main@x86_64 | — |
Vendor Fix
fix
Workaround
|
Threats
Impact
Moderate
References
39 references
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"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
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"threats": [
{
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"details": "Moderate"
}
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"title": "unbound: libngtcp2: Unbound: Denial of Service via assertion failure in DNS-over-QUIC environments"
},
{
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"discovery_date": "2026-07-20T21:24:56.694000+00:00",
"ids": [
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"text": "A flaw was found in Unbound, a domain name system (DNS) resolver. When Unbound is configured with DNSCrypt support, a remote attacker could send a specially crafted DNSCrypt query over TCP. This malicious query could cause a memory error, leading to a server crash and a Denial of Service (DoS). This means legitimate users would be unable to access services relying on the Unbound server.",
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"text": "This is an Important denial of service vulnerability affecting Unbound when built with DNSCrypt support. A remote attacker can trigger a heap overflow by sending a specially crafted DNSCrypt query over TCP, leading to a server crash and disruption of DNS resolution services. This vulnerability doesn\u0027t impact any supported the versions of unbound as shipped with Red Hat Enterprise Linux as it is not compiled with DNSCrypt support.",
"title": "Statement"
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{
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"text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
"title": "CVSS score applicability"
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},
"url": "https://access.redhat.com/errata/RHSA-2026:43588"
}
],
"scores": [
{
"cvss_v3": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"products": [
"Red Hat Hardened Images:unbound-main@aarch64",
"Red Hat Hardened Images:unbound-main@noarch",
"Red Hat Hardened Images:unbound-main@src",
"Red Hat Hardened Images:unbound-main@x86_64"
]
}
],
"threats": [
{
"category": "impact",
"details": "Important"
}
],
"title": "unbound: Unbound: Denial of Service via crafted DNSCrypt query"
},
{
"cve": "CVE-2026-56416",
"cwe": {
"id": "CWE-125",
"name": "Out-of-bounds Read"
},
"discovery_date": "2026-07-22T14:01:40.980897+00:00",
"ids": [
{
"system_name": "Red Hat Bugzilla ID",
"text": "2506137"
}
],
"notes": [
{
"category": "description",
"text": "A vulnerability in Unbound allows remote attackers using malicious DNSSEC-signed servers to send malformed records that trigger a heap buffer overflow. This can cause a denial of service or potential limited information disclosure.",
"title": "Vulnerability description"
},
{
"category": "summary",
"text": "unbound: Unbound: Heap buffer overflow via malformed DNSSEC record",
"title": "Vulnerability summary"
},
{
"category": "other",
"text": "This Moderate impact flaw in Unbound allows a remote attacker to trigger a heap buffer overflow by providing specially crafted DNSSEC records from a malicious authoritative server. This can lead to a denial of service for the Unbound service or potentially limited information disclosure. Exploitation requires the Unbound DNSSEC validator to process malformed records, which may be exacerbated if `msg-buffer-size` is configured below its default value.",
"title": "Statement"
},
{
"category": "general",
"text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
"title": "CVSS score applicability"
}
],
"product_status": {
"fixed": [
"Red Hat Hardened Images:unbound-main@aarch64",
"Red Hat Hardened Images:unbound-main@noarch",
"Red Hat Hardened Images:unbound-main@src",
"Red Hat Hardened Images:unbound-main@x86_64"
]
},
"references": [
{
"category": "self",
"summary": "Canonical URL",
"url": "https://access.redhat.com/security/cve/CVE-2026-56416"
},
{
"category": "external",
"summary": "RHBZ#2506137",
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2506137"
},
{
"category": "external",
"summary": "https://www.cve.org/CVERecord?id=CVE-2026-56416",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-56416"
},
{
"category": "external",
"summary": "https://nvd.nist.gov/vuln/detail/CVE-2026-56416",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56416"
},
{
"category": "external",
"summary": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-56416.txt",
"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-56416.txt"
}
],
"release_date": "2026-07-22T13:10:24.023000+00:00",
"remediations": [
{
"category": "vendor_fix",
"date": "2026-07-22T14:15:25+00:00",
"details": "For details on how to apply this update, which includes the changes described in this advisory, refer to:\nhttps://images.redhat.com/",
"product_ids": [
"Red Hat Hardened Images:unbound-main@aarch64",
"Red Hat Hardened Images:unbound-main@noarch",
"Red Hat Hardened Images:unbound-main@src",
"Red Hat Hardened Images:unbound-main@x86_64"
],
"restart_required": {
"category": "none"
},
"url": "https://access.redhat.com/errata/RHSA-2026:43588"
},
{
"category": "workaround",
"details": "To mitigate this issue, consider disabling DNSSEC validation in Unbound if it is not strictly required for your environment. This can be achieved by ensuring `module-config: \"iterator\"` is used in `unbound.conf` and that no `trust-anchor` or `auto-trust-anchor-file` directives are present. Disabling DNSSEC validation will reduce the security assurances provided by DNSSEC. Alternatively, configure Unbound to only perform DNSSEC validation for trusted zones. A restart of the Unbound service is required for changes to take effect.",
"product_ids": [
"Red Hat Hardened Images:unbound-main@aarch64",
"Red Hat Hardened Images:unbound-main@noarch",
"Red Hat Hardened Images:unbound-main@src",
"Red Hat Hardened Images:unbound-main@x86_64"
]
}
],
"scores": [
{
"cvss_v3": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 4.8,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L",
"version": "3.1"
},
"products": [
"Red Hat Hardened Images:unbound-main@aarch64",
"Red Hat Hardened Images:unbound-main@noarch",
"Red Hat Hardened Images:unbound-main@src",
"Red Hat Hardened Images:unbound-main@x86_64"
]
}
],
"threats": [
{
"category": "impact",
"details": "Moderate"
}
],
"title": "unbound: Unbound: Heap buffer overflow via malformed DNSSEC record"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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