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.
Weakness
The product checks the state of a resource before using that resource, but the resource’s state can change between the check and the use in a way that invalidates the results of the check.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Rsync | Samba | * | 3.4.3 (excluding) |
| Red Hat Enterprise Linux 10 | RedHat | rsync-0:3.4.4-1.el10_2 | * |
| Red Hat Enterprise Linux 8 | RedHat | rsync-0:3.1.3-27.el8_10 | * |
| Red Hat Enterprise Linux 9 | RedHat | rsync-0:3.2.5-7.el9_8.2 | * |
| Red Hat Enterprise Linux 9 | RedHat | rsync-0:3.2.5-7.el9_8.2 | * |
| Red Hat Discovery 2 | RedHat | discovery/discovery-ui-rhel9:1782166952 | * |
| Rsync | Ubuntu | devel | * |
| Rsync | Ubuntu | esm-infra-legacy/trusty | * |
| Rsync | Ubuntu | esm-infra-legacy/xenial | * |
| Rsync | Ubuntu | esm-infra/bionic | * |
| Rsync | Ubuntu | esm-infra/focal | * |
| Rsync | Ubuntu | esm-infra/xenial | * |
| Rsync | Ubuntu | jammy | * |
| Rsync | Ubuntu | noble | * |
| Rsync | Ubuntu | questing | * |
| Rsync | Ubuntu | resolute | * |
| Rsync | Ubuntu | upstream | * |
Potential Mitigations
Related Attack Patterns
References
- https://github.com/RsyncProject/rsync/pull/895/changes/8471fdd1561049ef5f58df44a1811a50bd9a531d
- https://github.com/RsyncProject/rsync/releases/tag/v3.4.3
- https://michael.stapelberg.ch/posts/2026-05-24-minimal-memory-safe-go-rsync-vulns/
- https://www.vulncheck.com/advisories/rsync-toctou-race-condition-allows-symlink-based-arbitrary-file-write
- https://access.redhat.com/errata/RHSA-2026:26332
- https://access.redhat.com/errata/RHSA-2026:26408
- https://access.redhat.com/errata/RHSA-2026:26410
- https://access.redhat.com/errata/RHSA-2026:29197
- https://access.redhat.com/security/cve/CVE-2026-29518
- https://bugzilla.redhat.com/show_bug.cgi?id=2469055
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-29518.json