CVE-2026-41051: TOCTOU in csync2
Platform
linux
Component
csync2
Fixed in
2.0+git.1600444747.83b3644-3.1
CVE-2026-41051 describes a Time-of-Check-Time-of-Use (TOCTOU) vulnerability discovered in csync2. This flaw arises due to the insecure handling of temporary directories when the software is compiled using C99 or later standards. Successful exploitation could allow an attacker to manipulate temporary files, potentially leading to unauthorized access or modification of data. Affected versions include 2.0+git.1600444747.83b3644-3.1–2.0+git.1600444747.83b3644-3.1, with a fix available in version 2.0+git.1600444747.83b3644-3.1.
Impact and Attack Scenarios
The TOCTOU vulnerability in csync2 allows an attacker to exploit a race condition during the creation and use of temporary files. By manipulating the filesystem between the time a file is checked for existence and the time it is used, an attacker can potentially overwrite or replace critical files with malicious content. This could lead to arbitrary code execution, data corruption, or denial of service. The specific impact depends on how csync2 utilizes these temporary files within its operations. A successful attack could compromise the integrity of the data being synchronized and potentially grant the attacker control over the system running csync2.
Exploitation Context
CVE-2026-41051 was published on 2026-05-13. Its severity is currently assessed as Medium (CVSS score of 5). There is no indication of this vulnerability being actively exploited in the wild or appearing on KEV/EPSS. Public proof-of-concept (POC) code is currently unavailable, but the TOCTOU nature of the vulnerability suggests that exploitation is possible with sufficient effort.
Threat Intelligence
Exploit Status
EPSS
0.01% (2% percentile)
CISA SSVC
CVSS Vector
What do these metrics mean?
- Attack Vector
- Local — attacker needs a local shell or interactive session on the system.
- Attack Complexity
- Low — no special conditions required. Attacker can exploit reliably without depending on rare configurations or timing.
- Privileges Required
- Low — any valid user account is sufficient. Basic authenticated access required.
- User Interaction
- Required — victim must take an action: open a file, click a link, or visit a crafted page.
- Scope
- Unchanged — impact is limited to the vulnerable component itself.
- Confidentiality
- None — no confidentiality impact. Attacker cannot read protected data.
- Integrity
- None — no integrity impact. Attacker cannot modify data.
- Availability
- High — complete crash or resource exhaustion. Full denial of service.
Affected Software
Timeline
- Reserved
- Published
- EPSS updated
Mitigation and Workarounds
The primary mitigation for CVE-2026-41051 is to upgrade to version 2.0+git.1600444747.83b3644-3.1 or later, which contains the fix. If an immediate upgrade is not feasible, consider implementing stricter file permissions on the temporary directories used by csync2 to limit the potential impact of a successful attack. Review the csync2 configuration to ensure that temporary directories are not world-writable. Monitor system logs for any unusual file access patterns or modifications within the temporary directories. After upgrade, confirm the fix by attempting to create a symbolic link to a temporary file while csync2 is running and verifying that the operation fails.
How to fix
Actualice a la versión 2.0.1 o posterior para mitigar el riesgo de ataques TOCTOU en los directorios temporales. La vulnerabilidad se debe a un uso inseguro de directorios temporales al compilar con C99 o versiones posteriores. Asegúrese de aplicar la actualización en todos los sistemas afectados.
Frequently asked questions
What is CVE-2026-41051 — TOCTOU in csync2?
CVE-2026-41051 is a Time-of-Check-Time-of-Use vulnerability in csync2, allowing attackers to manipulate temporary files and potentially compromise the system.
Am I affected by CVE-2026-41051 in csync2?
You are affected if you are running csync2 versions 2.0+git.1600444747.83b3644-3.1–2.0+git.1600444747.83b3644-3.1. Check your version with csync2 --version.
How do I fix CVE-2026-41051 in csync2?
Upgrade to version 2.0+git.1600444747.83b3644-3.1 or later. If immediate upgrade isn't possible, restrict permissions on temporary directories.
Is CVE-2026-41051 being actively exploited?
There is currently no public evidence of CVE-2026-41051 being actively exploited, but the TOCTOU nature makes exploitation possible.
Where can I find the official csync2 advisory for CVE-2026-41051?
Refer to the official csync2 project website or relevant security mailing lists for the advisory related to CVE-2026-41051.
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