Security readout for executives and security teams
Plain-English summary
This CVE affects CZ.NIC Knot Resolver before 4.3.0. A specially large DNS reply with many resource records can make the resolver spend excessive CPU time, slowing or denying DNS service. The business impact is availability: users and applications may fail to resolve names if vulnerable resolvers are overloaded.
Executive priority
Treat as a high-priority availability risk for DNS infrastructure. Patch exposed or critical resolvers promptly, but do not assume data theft or active exploitation from the provided evidence.
Technical view
CVE-2019-19331 is an unauthenticated network denial-of-service issue in Knot Resolver. The source describes inefficient processing of DNS replies containing very many resource records, classified as CWE-407. CVSS 3.0 is 7.5 with high availability impact and no confidentiality or integrity impact.
Likely exposure
Exposure is most likely where Knot Resolver versions before 4.3.0 are deployed, especially internet-facing or high-volume recursive DNS infrastructure that processes untrusted DNS responses.
Exploitation context
The provided bundle does not show CISA KEV listing or confirmed active exploitation. The attack context is network-based availability disruption through expensive processing of unusually record-heavy DNS replies.
Researcher notes
Evidence supports an algorithmic-complexity DoS, not code execution. The source bundle gives impact mechanics and fixed-version direction, but not detailed affected package matrices across all distributions or exploitation-in-the-wild evidence.
Mitigation direction
- Upgrade Knot Resolver to version 4.3.0 or a vendor-supported fixed package.
- Apply relevant distribution security updates, including Debian packages where applicable.
- Prioritize externally reachable or business-critical DNS resolver deployments.
- Review CZ.NIC and operating-system vendor guidance for supported fixed versions.
Validation and detection
- Inventory systems running Knot Resolver and record installed versions.
- Confirm no production resolver remains below version 4.3.0 unless vendor-backported fixes apply.
- Check package changelogs or advisories for CVE-2019-19331 fix confirmation.
- Review resolver CPU and availability monitoring for unexplained spikes or saturation.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-407: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2019-19331 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
7.5HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-19331CVE reference
- https://www.knot-resolver.cz/2019-12-04-knot-resolver-4.3.0.htmlCVE reference
- [debian-lts-announce] 20240426 [SECURITY] [DLA 3795-1] knot-resolver security updateCVE reference · mailing-list
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Inefficient Algorithmic Complexity
Inefficient Algorithmic Complexity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.