Rsync RCE and path traversal flaws affect backup systems
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Six Rsync vulnerabilities including heap overflow and path traversal enable remote code execution; patch to 3.4.0 immediately.
CIS/CERT issued advisory 2025-007 documenting six vulnerabilities in Rsync prior to version 3.4.0. The most severe, a heap buffer overflow (CVE-2024-12084) arising from improper checksum length handling in the daemon, allows remote code execution. Additional critical issues include an information leak via uninitialized stack data (CVE-2024-12085), arbitrary client file reconstruction by malicious servers (CVE-2024-12086), path traversal via the --inc-recursive option (CVE-2024-12087), bypass of the --safe-links protection (CVE-2024-12088), and a symbolic link race condition (CVE-2024-12747). Rsync is widely deployed in backup and file-transfer infrastructure including Rclone, DeltaCopy, ChronoSync, cloud storage, and server management systems. Successful exploitation allows code execution in the privilege context of the running process, permitting program installation, data theft, modification, or deletion. Exploitation impact scales with system privilege level; administrative contexts pose highest risk. The advisory recommends immediate patching to 3.4.0, vulnerability scanning, network segmentation, and least-privilege deployment. No active in-the-wild exploitation is reported.
Mentioned in this report
Detection guidance
Rsync Daemon or Process Spawning Shell on Linux
Detects rsync or rsyncd spawning a shell or interpreter, a post-exploitation indicator for heap overflow RCE in the rsync daemon (CVE-2024-12084 family). Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Rsync Daemon or Process Spawning Shell on Linux
description: Detects rsync/rsyncd as the parent of a shell or script interpreter.
Successful exploitation of the rsync daemon heap overflow (CVE-2024-12084) yields
code execution in the daemon's context, which commonly appears as a shell child
of the rsync process. Rsync itself rarely spawns shells.
tags:
- attack.initial-access
- attack.t1190
- attack.execution
logsource:
category: process_creation
product: linux
detection:
selection:
ParentImage|endswith:
- /rsync
- /rsyncd
Image|endswith:
- /sh
- /bash
- /dash
- /zsh
- /ksh
- /python
- /python3
- /perl
filter_exec_hooks:
CommandLine|contains:
- pre-xfer
- post-xfer
condition: selection and not filter_exec_hooks
falsepositives:
- rsync daemon modules configured with pre-xfer or post-xfer exec scripts that run
via a shell
- Backup wrappers invoking rsync with a custom remote shell command (-e) implemented
as a shell script
level: medium
id: b6303df8-e65e-5c64-b178-f48de4330cad
status: experimental
author: Vorant
references:
- https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-rsync-could-allow-for-remote-code-execution_2025-007
Rsync Daemon or Windows Rsync Port Spawning Command Interpreter
Detects rsync.exe (including DeltaCopy/Cygwin builds) spawning cmd, PowerShell or other LOLBins, suggesting exploitation of the rsync daemon. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Rsync Daemon or Windows Rsync Port Spawning Command Interpreter
description: Detects Windows rsync builds (such as Cygwin or DeltaCopy packaged rsync)
spawning a command interpreter or script host. This is a post-exploitation indicator
for RCE in rsync prior to 3.4.0 (CVE-2024-12084).
tags:
- attack.initial-access
- attack.t1190
- attack.execution
logsource:
category: process_creation
product: windows
detection:
selection:
ParentImage|endswith:
- \rsync.exe
- \rsyncd.exe
Image|endswith:
- \cmd.exe
- \powershell.exe
- \pwsh.exe
- \wscript.exe
- \cscript.exe
- \mshta.exe
- \certutil.exe
- \bitsadmin.exe
condition: selection
falsepositives:
- Backup jobs configured with pre or post transfer scripts launched through cmd.exe
- Administrators running rsync from an interactive shell wrapper that appears as parent
level: high
id: e60654b0-8bae-509c-94dc-f17fe676e96b
status: experimental
author: Vorant
references:
- https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-rsync-could-allow-for-remote-code-execution_2025-007
Rsync Invoked With Path Traversal Sequences in Arguments
Detects rsync command lines containing parent-directory traversal combined with recursion or link options, relevant to CVE-2024-12087/12088 abuse. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Rsync Invoked With Path Traversal Sequences in Arguments
description: Detects rsync executions on Linux whose arguments include directory traversal
sequences together with options tied to the path traversal and safe-links bypass
flaws (CVE-2024-12087, CVE-2024-12088). Needs tuning where relative paths are used
in backup scripts. Hunting-oriented.
tags:
- attack.initial-access
- attack.t1190
logsource:
category: process_creation
product: linux
detection:
selection_img:
Image|endswith: /rsync
selection_traversal:
CommandLine|contains:
- /../
- ' ../../'
selection_opts:
CommandLine|contains:
- --inc-recursive
- --safe-links
- --links
- ' -a'
- ' -r'
condition: selection_img and selection_traversal and selection_opts
falsepositives:
- Backup or deployment scripts that legitimately use relative source or destination
paths with parent directory references
- Developers syncing project trees with relative paths
level: low
id: b939bd62-4ef1-5c99-b847-0fc8c5fdb05f
status: experimental
author: Vorant
references:
- https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-rsync-could-allow-for-remote-code-execution_2025-007
Behavioural rules are generated from public reporting — validate in your environment before deploying.
Source reporting: https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-rsync-could-allow-for-remote-code-execution_2025-007
What this brief leaves out
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