CVE-2026-77059

TOCTOU Race Condition in boneIO

Published Oct 26, 2026 CVSS 4.0 · 8.8 High EPSS < 1% KEV · Not listed
Description
boneIO Black contains a TOCTOU race condition in the create_timedatectl_sudoers_file() function in boneio/webui/routes/timezone_sudoers.py. The function writes sudoers rules to a predictable temporary file, validates them, then installs them with root privileges. A local attacker can exploit the race window between validation and installation to substitute malicious content, or use the predictable filename for symlink attacks, resulting in arbitrary sudoers rule injection and local privilege escalation to root.

This issue was fixed in version 1.6.0.

Analysis

AI-generated

Technical impact

boneIO Black includes a time‑of‑check to time‑of‑use (TOCTOU) race condition in a function that creates a temporary sudoers file and later installs it with root privileges. During the brief period between validating the file’s contents and installing it, a local attacker can replace the temporary file with malicious content or create a symbolic link that points to an arbitrary location. If successful, the attacker injects arbitrary sudoers rules, giving them root access on the host.

Affected Systems

The vulnerability affects the boneIO boneIO product, specifically versions earlier than 1.6.0. Upgrade to 1.6.0 or later is required to remove the insecure file handling.

Risk and Exploitability

The CVSS score of 8.8 categorizes this bug as high risk, and although an EPSS score is not available, the lack of KEV listing does not diminish its danger. The flaw requires a local attacker with the ability to run code on the affected host to exploit the race window. Once the attack succeeds, the attacker gains unrestricted root privileges, enabling any system compromise.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade boneIO boneIO to version 1.6.0 or newer to eliminate the TOCTOU flaw.
  • Ensure the temporary directory used by boneIO has restricted write permissions and is not writable by unprivileged users, reducing the likelihood of symlink attacks.
  • Regularly audit the system’s sudoers file for unexpected changes, and monitor for modifications to temporary files created by boneIO.

Generated by OpenCVE AI on October 26, 2026 at 16:43 UTC.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description boneIO Black contains a TOCTOU race condition in the create_timedatectl_sudoers_file() function in boneio/webui/routes/timezone_sudoers.py. The function writes sudoers rules to a predictable temporary file, validates them, then installs them with root privileges. A local attacker can exploit the race window between validation and installation to substitute malicious content, or use the predictable filename for symlink attacks, resulting in arbitrary sudoers rule injection and local privilege escalation to root. This issue was fixed in version 1.6.0.
Title TOCTOU Race Condition in boneIO
First Time appeared Boneio
Boneio boneio
Weaknesses CWE-367
CPEs cpe:2.3:a:boneio:boneio:*:*:*:*:*:*:*:*
Vendors & Products Boneio
Boneio boneio
References
Metrics cvssV4_0

{'score': 8.8, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H'}

Weaknesses
  • CWE-367

    Time-of-check Time-of-use (TOCTOU) Race Condition

Sources

Status
PUBLISHED
Assigner
CERT-PL
Published
Updated
Oct 26, 2026, 3:35 PM
Reserved
Aug 20, 2026, 9:37 AM
Status
Deferred
Published
Oct 26, 2026, 3:16 PM
Modified
Oct 26, 2026, 5:11 PM