CVE-2026-93404
Description
A flaw was found in rsyslog. The built-in ClickHouse output templates fail to properly escape backslash characters when formatting Structured Query Language (SQL) queries. An attacker capable of submitting crafted log messages routed to an affected ClickHouse action can exploit this issue to alter executed SQL commands, potentially leading to unauthorized database modification or information disclosure.
Statement
Red Hat has rated this vulnerability as Important because a sender capable of submitting crafted log events can inject arbitrary SQL commands into the backend database, potentially compromising data integrity and confidentiality. The flaw specifically affects instances configured with the ClickHouse output module (omclickhouse), which is not active in default rsyslog installations and must be explicitly configured in deployment rulesets. Deployments that do not forward log messages to ClickHouse or that only ingest logs from trusted local sources have significantly reduced exposure.
Mitigation
To mitigate this issue, disable the ClickHouse output module or comment out all action directives utilizing 'omclickhouse' within /etc/rsyslog.conf and /etc/rsyslog.d/.
After modifying the configuration, restart the rsyslog service:
systemctl restart rsyslog
Warning: Restarting the rsyslog service briefly interrupts log processing, and disabling the omclickhouse action stops forwarding log records to the ClickHouse database.
If forwarding cannot be disabled, restrict remote access to rsyslog ingestion ports (such as UDP/TCP port 514) to trusted network hosts using firewall rules to prevent unauthorized message submission.
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 | 8.1 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | High | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | High | N/A | N/A |
| Integrity Impact | High | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability
Technical Impact: Execute Unauthorized Code or Commands
Adversaries could execute system commands, typically by changing the SQL statement to redirect output to a file that can then be executed.
Confidentiality
Technical Impact: Read Application Data
Since SQL databases generally hold sensitive data, loss of confidentiality is a frequent problem with SQL injection vulnerabilities.
Authentication
Technical Impact: Gain Privileges or Assume Identity; Bypass Protection Mechanism
If poor SQL commands are used to check user names and passwords or perform other kinds of authentication, it may be possible to connect to the product as another user with no previous knowledge of the password.
Access Control
Technical Impact: Bypass Protection Mechanism
If authorization information is held in a SQL database, it may be possible to change this information through the successful exploitation of a SQL injection vulnerability.
Integrity
Technical Impact: Modify Application Data
Just as it may be possible to read sensitive information, it is also possible to modify or even delete this information with a SQL injection attack.
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