Full Report
CVE-2025-61915 is a stack-based out-of-bounds write bug in CUPS (Common Unix Printing System). When exploited, an unauthorized user can modify cupsd.conf and add a malicious IPv6 address. CUPS, the printing stack in Unix, will parse the IPv6 incorrectly, causing a stack underflow.
Analysis Summary
# Vulnerability: CUPS Stack-Based Buffer Underflow in IPv6 Parsing
## CVE Details
- **CVE ID:** CVE-2025-61915
- **CVSS Score:** Pending (High/Critical potential based on impact)
- **CWE:** CWE-121 (Stack-based Buffer Overflow) / CWE-124 (Buffer Underwrite)
## Affected Systems
- **Products:** CUPS (Common Unix Printing System)
- **Versions:** Affected versions typically include current distributions of OpenPrinting CUPS prior to the release of official patches.
- **Configurations:** Systems where an unauthorized or local user has the ability to modify or influence the `cupsd.conf` configuration file.
## Vulnerability Description
CVE-2025-61915 is a stack-based out-of-bounds write (specifically a buffer underflow) occurring within the `cupsd` daemon. The flaw is triggered when the software attempts to parse a specially crafted, malicious IPv6 address within the configuration file (`cupsd.conf`).
Due to improper validation of the IPv6 structure, the parsing logic calculates a memory offset incorrectly. This leads to a stack underflow, allowing an attacker to overwrite adjacent memory on the stack with controlled data. This memory corruption can be leveraged to redirect execution flow.
## Exploitation
- **Status:** PoC available (demonstrated by security researchers to execute arbitrary code as root).
- **Complexity:** Medium
- **Attack Vector:** Local (Requires the ability to modify `cupsd.conf` or exploit a secondary service that can write to the CUPS configuration).
## Impact
- **Confidentiality:** High (Potential to read sensitive memory)
- **Integrity:** High (Successful exploitation allows for unauthorized modification of system files and memory)
- **Availability:** High (Can lead to daemon crashes or full system takeover)
- **Root Elevation:** Exploitation allows for arbitrary code execution with **root** privileges.
## Remediation
### Patches
- Users should update to the latest version of CUPS provided by their Linux distribution or from the OpenPrinting GitHub repository immediately upon release.
### Workarounds
- Restrict write access to `cupsd.conf` to the absolute minimum necessary users.
- Implement strict filesystem permissions and use Mandatory Access Control (MAC) systems like SELinux or AppArmor to confine the `cupsd` process.
## Detection
- **Indicators of Compromise:** Unusual IPv6 addresses in `cupsd.conf` containing long sequences of colons or non-standard characters (e.g., `:ffff:7fff::...`).
- **Detection Methods:**
- Monitor `cupsd` for unexpected crashes (SIGSEGV).
- Use system auditing tools (like `auditd` or `sysdig`) to monitor unauthorized modifications to `/etc/cups/cupsd.conf`.
- Scan logs for errors related to "Invalid address" or memory corruption alerts from the CUPS daemon.
## References
- LevelBlue SpiderLabs Advisory: hxxps[://]www[.]levelblue[.]com/blogs/spiderlabs-blog/cve-2025-61915-buffer-underflow-vulnerability-leads-to-memory-corruption-in-cups
- OpenPrinting CUPS GitHub: hxxps[://]github[.]com/OpenPrinting/cups