CVE-2026-29518
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.15%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 4.0
- 7.3 HIGHCVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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/M
- EPSS
- 0.15% probability · 5th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-367
- Affected
- samba/rsync
- Source
- disclosure@vulncheck.com
References
- https://github.com/RsyncProject/rsync/pull/895/changes/8471fdd1561049ef5f58df44a1811a50bd9a531dPatch
- https://github.com/RsyncProject/rsync/releases/tag/v3.4.3Release Notes
- 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-writeThird Party Advisory
- 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/errata/RHSA-2026:54769
- 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.