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symlink races on path-based syscalls

Moderate
tridge published GHSA-4h9m-w5ff-j735 May 20, 2026

Package

rsync

Affected versions

< 3.4.3

Patched versions

>= 3.4.3

Description

Impact

previous bug fixes for symlink races in open() calls missed races in other path based system calls like chmod() and chown(). For rsync daemons with "use chroot = no" this allows an attacker with local filesystem access to change permissions, ownership or timestamp on a file outside the exported module.
This impacts the following system calls:

  • chmod set_file_attrs() applies the sender-supplied mode
  • lchown set_file_attrs() applies the sender-supplied owner
  • utimes set_file_attrs() applies the sender-supplied mtime
  • rename the central tmp -> final rename in finish_transfer()
  • unlink delete or partial-file cleanup
  • mkdir create directory entries from the sender's file list
  • symlink create symlink entries
  • mknod create device entries
  • link hard-link from --link-dest basis to destination
  • rmdir --delete cleanup
  • lstat pre-transfer dest inspection in the generator

Patches

Fixes are in the 3.4.3 release

Workarounds

ensure that "use chroot" is left at the default value of yes

References

https://rsync.samba.org

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

CVE ID

CVE-2026-43619

Weaknesses

Improper Link Resolution Before File Access ('Link Following')

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource. Learn more on MITRE.

Time-of-check Time-of-use (TOCTOU) Race Condition

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. Learn more on MITRE.

Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. Learn more on MITRE.

Credits