CVE-2026-7771 Overview
CVE-2026-7771 affects IBM Db2 versions 11.5.0 through 11.5.9 and 12.1.0 through 12.1.4. The vulnerability allows an authenticated local user to trigger a trap condition when Db2 compiles a specially crafted SQL statement containing subqueries. Successful exploitation causes a denial of service against the database engine. IBM has assigned this issue to the loop with unreachable exit condition weakness class [CWE-835].
Critical Impact
A local user submitting a malformed subquery can crash the Db2 query compiler and disrupt availability for all connected database clients.
Affected Products
- IBM Db2 11.5.0 through 11.5.9
- IBM Db2 12.1.0 through 12.1.4
- Db2 deployments on all supported operating system platforms
Discovery Timeline
- 2026-07-17 - CVE-2026-7771 published to NVD
- 2026-07-24 - Last updated in NVD database
Technical Details for CVE-2026-7771
Vulnerability Analysis
CVE-2026-7771 is a denial of service vulnerability in the IBM Db2 SQL statement compiler. When the compiler processes a crafted statement that embeds specific subquery constructs, it enters a state that triggers an internal trap. The engine terminates the offending session and can disrupt the query compilation subsystem, breaking availability for concurrent workloads.
The defect is classified under [CWE-835], loop with unreachable exit condition. The compilation path fails to bound its analysis of the nested subquery structure. IBM has published fixed builds and a security bulletin describing affected components in the IBM Support Page.
Root Cause
The vulnerability stems from improper handling of nested subquery expressions during statement compilation. Certain input shapes cause the compiler to hit an unrecoverable condition rather than returning a controlled SQL error. Because the failure occurs before execution, standard query permissions do not gate the crash. Any account able to submit SQL to the affected instance can reach the vulnerable code path.
Attack Vector
Exploitation requires a local attack vector with user interaction, but no authentication privileges beyond the ability to submit SQL. An attacker with a valid database session sends a crafted SELECT containing the offending subquery pattern. The Db2 compiler traps on parse or semantic analysis, and the outcome is loss of availability rather than data disclosure or integrity impact. The EPSS score of 0.103% reflects a low observed likelihood of exploitation.
No public proof-of-concept code is available at this time. Refer to the IBM Support Page for vendor technical details.
Detection Methods for CVE-2026-7771
Indicators of Compromise
- Repeated db2diag.log trap entries referencing SQL compiler or parser modules
- Unexpected SQL1224N or agent termination errors following complex SELECT statements
- Crash dumps or FODC_Trap directories generated under the Db2 instance diagnostic path
- Client applications reporting lost connections tied to specific SQL statements containing nested subqueries
Detection Strategies
- Parse Db2 diagnostic logs for trap signatures correlated with statement compilation events
- Alert on SQL statement identifiers that repeatedly precede engine trap or agent restart entries
- Baseline normal query compilation error rates and flag deviations from anonymous or low-privilege accounts
Monitoring Recommendations
- Forward db2diag.log, audit logs, and FODC directories to a centralized logging platform for correlation
- Track database availability metrics and agent restart counts to identify DoS attempts early
- Review Db2 audit trails for accounts issuing malformed or highly nested SQL against production instances
How to Mitigate CVE-2026-7771
Immediate Actions Required
- Apply the fix pack referenced in the IBM security bulletin for your Db2 11.5.x or 12.1.x branch
- Restrict SQL submission privileges on affected instances to trusted application accounts only
- Enable Db2 audit logging for statement compilation failures on production databases
Patch Information
IBM has released fixed builds addressing CVE-2026-7771 for Db2 11.5 and Db2 12.1. Consult the IBM Support Page for the exact fix pack levels, download links, and installation guidance. Upgrade Db2 11.5.0 through 11.5.9 and Db2 12.1.0 through 12.1.4 instances to the vendor-supplied patched releases.
Workarounds
- Limit local and remote database logins to vetted service accounts until patches are deployed
- Route application traffic through parameterized queries and reject ad-hoc SQL from untrusted users
- Monitor and rate-limit sessions producing repeated compilation traps, terminating offending connections
# Verify current Db2 version and plan upgrade to the fixed level
db2level
# Review the IBM advisory for the fix pack matching your branch
# https://www.ibm.com/support/pages/node/7279480
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
