Security readout for executives and security teams
Plain-English summary
CVE-2026-21948 is a denial-of-service flaw in Oracle MySQL Server’s optimizer. A highly privileged attacker with network access can make the database hang or crash repeatedly. This does not indicate data theft or data modification, but it can disrupt applications that depend on affected MySQL versions.
Executive priority
Treat as a service availability risk for systems depending on affected MySQL versions. Prioritize exposed or business-critical databases, especially where many users or applications hold elevated database privileges. No sourced evidence indicates data compromise or active exploitation.
Technical view
Oracle reports the flaw affects MySQL Server 8.0.0-8.0.44, 8.4.0-8.4.7, and 9.0.0-9.5.0 in the Server: Optimizer component. CVSS is 4.9: network reachable, low complexity, high privileges required, no user interaction, and high availability impact. CWE is CWE-400.
Likely exposure
Exposure is limited to MySQL Server instances where an attacker already has high privileges and network access over supported MySQL protocols. Internet exposure increases operational risk, but privilege requirements substantially reduce likelihood.
Exploitation context
The provided sources do not show active exploitation, and this CVE is not marked in CISA KEV. Oracle describes it as easily exploitable once high privileges and network access are present. Impact is complete denial of service through hangs or repeatable crashes.
Researcher notes
The source bundle identifies only Oracle MySQL Server and the optimizer component. It does not include root-cause details, proof-of-concept status, fixed version numbers, or workaround specifics beyond Oracle’s advisory reference. Avoid assuming exploit availability or behavior beyond denial of service.
Mitigation direction
- Review Oracle’s January 2026 Critical Patch Update for affected MySQL Server versions.
- Apply Oracle-provided updates or version guidance when available for your deployment branch.
- Restrict network access to MySQL Server to trusted application and administration paths.
- Limit high-privilege database accounts and review unnecessary elevated access.
- Ensure monitoring alerts on MySQL hangs, restarts, and repeated crash loops.
Validation and detection
- Inventory MySQL Server versions and compare against Oracle’s affected ranges.
- Identify instances reachable over networks by non-administrative or broad user groups.
- Review accounts with high MySQL privileges and validate business need.
- Check database logs and service monitoring for repeated optimizer-related crashes or hangs.
- Confirm remediation status against Oracle’s advisory after patching or upgrading.
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-2026-21948 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
- 4.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:H/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:H/UI:N/S:U/C:N/I:N/A:H1.23.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.9MediumVector: CVSS:3.1/AV:N/AC:L/PR:H/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.