CVE-2026-43618: Rsync integer overflow in compressed-token decoder

CVE-2026-43618 · Severity: high · CVSS 8.1 · Published 2026-05-20

Rsync is a widely used utility for efficiently transferring and synchronizing files between systems. A security flaw in its data compression component allows a remote attacker to trick the system into leaking sensitive information from its memory. This could result in the exposure of passwords, environment variables, and other internal data, which could be used to bypass security protections or gain further access to the server.

Technologies: RsyncProject Rsync. Vendors: RsyncProject.

Quick answers

Is CVE-2026-43618 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-43618 being exploited in the wild.
How severe is CVE-2026-43618?
High severity, with a CVSS score of 8.1, published 20 May 2026.
Which products and versions are affected?
RsyncProject Rsync <= 3.4.2.
Is there a fix for CVE-2026-43618?
A patch was published on 2026-05-20: Rsync version 3.4.3 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-43618 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-43618?
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

An integer overflow vulnerability exists in the rsync receiver's compressed-token decoder. The component uses a 32-bit signed counter to accumulate tokens without performing overflow checks. A malicious sender can provide crafted input to trigger this overflow, leading to an out-of-bounds read (CWE-125). An authenticated attacker can exploit this to leak process memory, including heap and stack data, environment variables, and library pointers. This information disclosure can be used to defeat ASLR or extract credentials. The vulnerability is fixed in version 3.4.3; a known workaround is to disable compression by setting 'refuse options = compress' in the rsyncd.conf configuration.

Affected products

  • RsyncProject rsync <= 3.4.2

Timeline

  • 2026-05-19: disclosed: Initial disclosure by VulnCheck
  • 2026-05-20: patched: Rsync version 3.4.3 released
  • 2026-05-20: advisory: GitHub Security Advisory published

References

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