CVE-2026-48693

Description

FastNetMon Community Edition through 1.2.9 is vulnerable to a local symlink attack via predictable file paths in /tmp. The statistics file path defaults to '/tmp/fastnetmon.dat' (src/fastnetmon.cpp line 159). The print_screen_contents_into_file() function (src/fastnetmon_logic.cpp line 2186) opens this path with std::ios::trunc without checking for symlinks or using O_NOFOLLOW. Additionally, the chmod() call on line 2190 always operates on cli_stats_file_path regardless of which file_path parameter was passed (a bug that applies wrong permissions), and the umask is set to 0 during daemonization (src/fastnetmon.cpp line 1821), making all created files world-writable. A local attacker can exploit this to overwrite arbitrary files as the FastNetMon process user (typically root).

CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.04%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-59 CWE-59

Affected Products

Vendor	Product	Versions
pavel-odintsov	fastnetmon	< 1.2.9

References

Other References

https://github.com/pavel-odintsov/fastnetmon https://github.com/pavel-odintsov/fastnetmon/blob/master/src/fastnetmon.cpp https://github.com/pavel-odintsov/fastnetmon/blob/master/src/fastnetmon_logic.cpp https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48693-symlink-tmp

Frequently Asked Questions

What is CVE-2026-48693? +

FastNetMon Community Edition through 1.2.9 is vulnerable to a local symlink attack via predictable file paths in /tmp. The statistics file path defaults to '/tmp/fastnetmon.dat' (src/fastnetmon.cpp line 159). The print_screen_contents_into_file() function (src/fastnetmon_logic.cpp line 2186) opens this path with std::ios::trunc without checking for symlinks or using O_NOFOLLOW. Additionally, the chmod() call on line 2190 always operates on cli_stats_file_path regardless of which file_path parameter was passed (a bug that applies wrong permissions), and the umask is set to 0 during daemonization (src/fastnetmon.cpp line 1821), making all created files world-writable. A local attacker can exploit this to overwrite arbitrary files as the FastNetMon process user (typically root). It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-48693? +

CVE-2026-48693 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-48693? +

CVE-2026-48693 affects products from pavel-odintsov, specifically: fastnetmon. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-48693? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-30371

Metabase is a business intelligence and embedded analytics tool. Versions prior to v0.52.16.4, v1.52.16.4, v0.53.8, and v1.53.8 are vulnerable to …

CVE-2025-4211

Improper Link Resolution Before File Access ('Link Following') vulnerability in QFileSystemEngine in the Qt corelib module on Windows which potentially …

CVE-2025-2102

Improper Link Resolution Before File Access ('Link Following') vulnerability in HYPR Passwordless on Windows allows Privilege Escalation.This issue affects HYPR …

CVE-2025-52936

Improper Link Resolution Before File Access ('Link Following') vulnerability in yrutschle sslh.This issue affects sslh: before 2.2.2.

CVE-2025-53109

Model Context Protocol Servers is a collection of reference implementations for the model context protocol (MCP). Versions of Filesystem prior …

CVE-2025-7012

An issue in Cato Networks' CatoClient for Linux, before version 5.5, allows a local attacker to escalate privileges to root …