CVE-2026-43618

Rsync version 3.4.2 and prior contain an integer overflow vulnerability in the compressed-token decoder where a 32-bit signed counter is not checked for overflow, allowing a malicious sender to trigger an overflow that causes the receiver process to read and return data from outside the intended buffer bounds. Attackers can exploit this vulnerability to disclose process memory contents including environment variables, passwords, heap and stack data, and library memory pointers, significantly reducing ASLR effectiveness and facilitating further exploitation.

What this means for your business

It affects Samba Rsync. It matters if your company, or a supplier that handles your data, runs it.
An attacker can use it remotely, over a network, with an ordinary user login, and without anyone at your company clicking anything.
FIRST's prediction model gives it a 0.8% chance of attack attempts being seen in the next 30 days, ranking above 53% of all known flaws.

What to do

1Check whether your company or your suppliers run Samba Rsync, and which version. The affected versions are listed further down this page.
2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

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Scoring

CVSS: 8.1 (v3.1)
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
CVSS v4: 6.1
Weakness: CWE-125
Assigned by: disclosure@vulncheck.com

Dates

Published: 2026-05-20
Last modified: 2026-09-01
Sources: NVD

Affected products

Samba Rsync- 3.4.2

As listed in the NVD configuration data. Not a statement about your estate.