CVE-2026-39316
Description
A flaw was found in CUPS, an open-source printing system. This vulnerability, known as a use-after-free, occurs in the CUPS scheduler when temporary printers are automatically removed. The system fails to properly manage memory, leaving a pointer to a freed memory location. An attacker could exploit this to cause the CUPS daemon to crash, leading to a denial of service. In more severe scenarios, this could potentially allow an attacker to execute arbitrary code.
Statement
This Moderate impact vulnerability in CUPS arises from a use-after-free flaw within the scheduler when temporary printers are automatically deleted. Exploitation could lead to a denial of service of the CUPS daemon, and potentially arbitrary code execution. This affects Red Hat systems running CUPS where temporary printers are configured or utilized.
Mitigation
To mitigate this issue, restrict network access to the CUPS daemon to only trusted hosts or localhost. This can be achieved by configuring firewall rules to block access to TCP port 631 from untrusted networks. For example, using `firewalld`:
`sudo firewall-cmd --permanent --zone=public --remove-port=631/tcp`
`sudo firewall-cmd --reload`
Alternatively, configure CUPS to only listen on localhost by modifying the `Listen` directive in `/etc/cups/cupsd.conf` to `Listen localhost:631`. After modifying the configuration, the CUPS service must be restarted for changes to take effect, which may temporarily interrupt printing services:
`sudo systemctl restart cups`
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4 | 6.2 | 4 |
| Attack Vector | Local | Local | Local |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | Low | High | Low |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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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