# CVE-2026-29518: Rsync TOCTOU race condition in daemon file handling

Source: https://junglewise.ai/threats/cve-2026-29518-rsync-toctou-race-condition-in-daemon-file-handling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-20. Updated: 2026-05-20  
License: CC BY 4.0 with a link back

CVE-2026-29518 · Severity: high · CVSS 7 · Published 2026-05-20

Rsync is a widely used utility for synchronizing files between different locations or systems. A security flaw in how the rsync daemon handles files allows a local attacker to trick the system into writing files in unauthorized locations, such as sensitive system directories. This could lead to a full system takeover if the rsync service is running with high privileges and the 'chroot' security feature is disabled.

Technologies: [RsyncProject Rsync](https://junglewise.ai/threats/technologies/rsync). Vendors: [RsyncProject](https://junglewise.ai/threats/vendors/rsyncproject).

## Quick answers

**Is CVE-2026-29518 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-29518 being exploited in the wild.

**How severe is CVE-2026-29518?** High severity, with a CVSS score of 7, published 20 May 2026.

**Which products and versions are affected?** RsyncProject Rsync < 3.4.3.

**Is there a fix for CVE-2026-29518?** A patch was published on 2026-05-20: Fixed in version 3.4.3 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-29518 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-29518?** Check whether you run RsyncProject Rsync at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A time-of-check to time-of-use (TOCTOU) race condition exists in the rsync daemon's file handling logic. An attacker with write access to a module path can replace parent directory components with symbolic links during the small window between the daemon's path validation and the actual file operation. This allows the attacker to redirect file writes to arbitrary locations on the filesystem. The vulnerability is exploitable only when the 'chroot' setting is set to false. If the daemon is running with elevated privileges, this can result in arbitrary file creation or modification, leading to privilege escalation. The issue is addressed in version 3.4.3.

## Affected products

- RsyncProject rsync < 3.4.3

## Timeline

- 2026-05-20: disclosed
- 2026-05-20: patched: Fixed in version 3.4.3
- 2026-05-20: advisory

## References

- [https://github.com/RsyncProject/rsync/pull/895/changes/8471fdd1561049ef5f58df44a1811a50bd9a531d](https://github.com/RsyncProject/rsync/pull/895/changes/8471fdd1561049ef5f58df44a1811a50bd9a531d)
- [https://github.com/RsyncProject/rsync/releases/tag/v3.4.3](https://github.com/RsyncProject/rsync/releases/tag/v3.4.3)
- [https://www.vulncheck.com/advisories/rsync-toctou-race-condition-allows-symlink-based-arbitrary-file-write](https://www.vulncheck.com/advisories/rsync-toctou-race-condition-allows-symlink-based-arbitrary-file-write)

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