CVE intelligence and bounded remediation
CVE-2026-29518 — Samba Rsync security vulnerability
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.
- Severity
- High
- CVSS
- 7.8 (3.1)
- Published
- 2026-05-20
- CISA KEV
- Not currently listed
- Ecosystem
- software/application
- Weaknesses
- CWE-367
Affected products
- samba / rsync
Matched remediation archetype
Race condition, TOCTOU, and lifecycle synchronization
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Check exposure
- Map concurrent actors, shared state, lock boundaries, signals, callbacks, retries, and check-then-use sequences in the affected path.
- Determine whether untrusted users can influence timing, object names, filesystem state, or repeated state transitions.
- Identify clustered and multi-process behavior that repository-local tests may not represent.
Remediate safely
- Make the sensitive state transition atomic or protect it with a consistently ordered synchronization primitive.
- Perform authorization and invariant checks on the same authoritative object and transaction used for the operation.
- Use unique private resources, safe ownership transfer, and idempotent operations; add deterministic concurrency regression tests.
Authoritative sources
Complete CVE record and remediation plan
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