CVE-2026-116323
Description
A flaw was found in PostgreSQL. A use-after-free vulnerability in the PL/Tcl procedural language extension occurs when evaluating domain CHECK constraints that re-enter the Tcl interpreter. An authenticated database user with privileges to create objects can exploit this flaw to execute arbitrary code as the operating system user running the database service.
Statement
Red Hat rates this vulnerability as Important because an authenticated user with permission to create database objects can achieve arbitrary code execution under the postgres operating system account. In standard Red Hat Enterprise Linux deployments, the PL/Tcl procedural language is neither installed nor enabled by default, significantly limiting exposure on typical systems. Risk is primarily confined to environments where the optional PL/Tcl subpackage is explicitly installed and untrusted users have been granted object creation privileges.
Mitigation
If PL/Tcl is not required, remove the optional procedural language package or drop the extension from affected databases. Alternatively, restrict object creation permissions for untrusted database accounts.
1. To remove the optional PL/Tcl package:
# dnf remove postgresql-pltcl
2. To remove the extension from a specific database, execute the following SQL commands as a database administrator:
DROP EXTENSION IF EXISTS pltcl CASCADE;
DROP EXTENSION IF EXISTS pltclu CASCADE;
3. To prevent untrusted accounts from creating custom domains or objects, revoke schema creation privileges:
REVOKE CREATE ON SCHEMA <schema_name> FROM <username>;
Caveats:
Dropping the extension with CASCADE removes all dependent database functions, triggers, and objects implemented in PL/Tcl, which can impair application functionality. If package removal or administrative actions require reloading or restarting the PostgreSQL service (systemctl restart postgresql), active client connections will be terminated.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | N/A | 8.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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