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Description

Rsync versions before 3.4.3 contain a time-of-check to time-of-use (TOCTOU) race condition in daemon file handling that allows attackers to redirect file writes outside intended directories by replacing parent directory components with symbolic links. Attackers with write access to a module path can exploit this race condition to create or overwrite arbitrary files, potentially modifying sensitive system files and achieving privilege escalation when the daemon runs with elevated privileges. This vulnerability can only be triggered if the chroot setting is false.

PUBLISHED Reserved 2026-03-04 | Published 2026-05-20 | Updated 2026-05-20 | Assigner VulnCheck




HIGH: 7.3CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

HIGH: 7.0CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem types

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

Product status

Default status
unaffected

Any version before 3.4.3
affected

Credits

Nullx3D (Batuhan SANCAK) finder

Michael Stapelberg finder

Damien Neil finder

References

github.com/...anges/8471fdd1561049ef5f58df44a1811a50bd9a531d issue-tracking

github.com/RsyncProject/rsync/releases/tag/v3.4.3 release-notes

www.vulncheck.com/...lows-symlink-based-arbitrary-file-write third-party-advisory

cve.org (CVE-2026-29518)

nvd.nist.gov (CVE-2026-29518)

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