FedoraOperating system · Fedoraproject
CVE-2019-10191
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability was discovered in DNS resolver of knot resolver before version 4.1.0 which allows remote attackers to downgrade DNSSEC-secure domains to DNSSEC-insecure state, opening possibility of domain hijack using attacks against insecure DNS protocol.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA DNSSEC downgrade vulnerability in Knot Resolver before version 4.1.0 allows remote attackers to manipulate the resolver into treating DNSSEC-validated domains as insecure. This is achieved by exploiting how the resolver processes certain DNS responses, effectively stripping DNSSEC protection and enabling domain hijacking attacks via insecure DNS protocol.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FedoraOperating system
= 29= 30< 4.1.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify Knot Resolver is installedCheck for the knot-resolver package using your system package manager (e.g., `rpm -qa | grep knot-resolver` on Fedora/RHEL, or `dpkg -l | grep knot-resolver` on Debian/Ubuntu). Alternatively, run `knot-resolver --version` if the binary is in PATH.Affected if Knot Resolver package or binary is present on the system
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Determine installed Knot Resolver versionRun `knot-resolver --version` or check the package version via your package manager (e.g., `rpm -q knot-resolver` on Fedora, `apt-cache policy knot-resolver` on Debian).Affected if Version returned is lower than 4.1.0 (e.g., 4.0.x, 3.x, or any version number less than 4.1.0)
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Confirm DNSSEC validation is configuredInspect the Knot Resolver configuration file (typically `/etc/knot-resolver/kresd.conf` or `/etc/kresd.conf`) for DNSSEC-related settings. Look for directives such as `trust_anchors.file`, `validate` policy settings, or modules like `policy` and `dnssec` being loaded.Affected if DNSSEC validation is explicitly enabled in the resolver configuration (this makes the downgrade attack relevant)
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Check running resolver processIf Knot Resolver is running as a service, verify the active process with `ps aux | grep kresd` or `systemctl status knot-resolver` to confirm the daemon is active and using the affected binary.Affected if The running service is based on an affected version of Knot Resolver
The environment is affected if Knot Resolver version 4.1.0 or higher is not installed and DNSSEC validation is enabled in the configuration.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data4.1.0
Upgrade Knot Resolver to version 4.1.0 or later to obtain the patched code that properly validates DNSSEC trust chains.
Fix this in Fedora
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-10191 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2019-10191 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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