mport package installation has symlink TOCTOU in chown and chmod handling

published 2026-09-17 52 d ago modified 2026-09-18 51 d ago also EUVD-2026-82329

cvss: 5.8; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits: 0; none known

mport is the MidnightBSD Package Manager. Prior to 2.7.8, do_actual_install() in libmport/bundle_read_install_pkg.c used path-based lstat(), chown(), stat(), and chmod() operations while installing package files. A local attacker with write access to a target directory could replace a checked file with a symlink before privileged ownership or mode changes were applied, redirecting those changes to an attacker-selected path and compromising filesystem integrity or permissions. This issue is fixed in version 2.7.8.

Patch / fix

links 3

github.com/MidnightBSD/mport@4676ac0 commit
github.com/MidnightBSD/mport#150 pull request
github.com/MidnightBSD/mport/releases/tag/2.7.8 release

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 51 d ago (2026-09-18)

Exploit prediction

0.10% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	5.8	CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
CNA	4.0	5.8	CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

MidnightBSD mport

Classification

Weakness

CWE-59 Improper Link Resolution Before File Access
CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References

Sources

CVE List CVE-2026-54576
NVD CVE-2026-54576

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary