Security readout for executives and security teams
Plain-English summary
CVE-2026-21949 is a denial-of-service vulnerability in Oracle MySQL Server’s Optimizer component. A low-privileged attacker with network access can cause the database server to hang or crash repeatedly. This does not indicate data theft or data modification, but it can interrupt applications that depend on affected MySQL versions.
Executive priority
Treat as a timely availability risk for business systems relying on affected MySQL versions. Prioritize exposed production databases and shared environments where many low-privileged users or applications can connect.
Technical view
Oracle describes this as an easily exploitable MySQL Server Optimizer vulnerability affecting supported versions 9.0.0 through 9.5.0. The CVSS 3.1 score is 6.5 with AV:N/AC:L/PR:L/UI:N and high availability impact. CWE-400 indicates resource consumption behavior. Impact is complete denial of service through hangs or repeatable crashes.
Likely exposure
Exposure is most relevant where MySQL Server 9.0.0 through 9.5.0 is reachable over a network by low-privileged database users or application accounts. Internet-facing or broadly reachable database services carry higher operational risk.
Exploitation context
The provided sources do not show active exploitation, and the CVE is not marked KEV. Exploitation requires network access and low privileges, but no user interaction. The outcome described is service disruption, not confidentiality or integrity compromise.
Researcher notes
The bundle provides vendor-level impact and CVSS details but no exploit specifics or standalone mitigation text. The affected range appears in the description as 9.0.0-9.5.0; one affected entry lists 9.0.0, so confirm scope against Oracle’s advisory.
Mitigation direction
- Review Oracle’s January 2026 Critical Patch Update guidance for MySQL Server.
- Apply the vendor-provided update or remediation for affected supported versions.
- Restrict MySQL network access to trusted application hosts and administrators.
- Review and remove unnecessary low-privileged database accounts.
- Monitor MySQL availability, restarts, and crash logs for abnormal patterns.
Validation and detection
- Inventory MySQL Server instances and record exact versions.
- Identify systems running MySQL Server 9.0.0 through 9.5.0.
- Confirm whether Oracle CPU guidance has been applied.
- Verify MySQL is not reachable from untrusted networks.
- Review logs for repeated crashes, hangs, or unexpected restarts.
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-400: 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-2026-21949 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
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/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:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- Oracle AdvisoryCVE reference · vendor-advisory
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.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.