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RsyncApplication · Samba

CVE-2026-43620

MEDIUM · 5.5 CVSS v3.1 Published 2026-05-20
Fix available
A fix is available. Upgrade to after 3.4.2 or later.
See remediation →
58/100
Remediation priority · Elevated
No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Rsync version 3.4.2 and prior contain a receiver-side out-of-bounds array read vulnerability in recv_files() in receiver.c that allows a malicious rsync server to crash the rsync client process. Attackers can exploit the vulnerability by setting CF_INC_RECURSE in compatibility flags and sending a specially crafted file list where the first sorted entry is not the leading dot directory, followed by a transfer record with ndx=0 and an iflag word without ITEM_TRANSFER, causing the receiver to read 8 bytes before the allocated pointer array and dereference an invalid pointer at an unmapped address, resulting in a deterministic SIGSEGV crash of the rsync client.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Rsync versions 3.4.2 and prior contain a receiver-side out-of-bounds array read vulnerability in recv_files() in receiver.c. A malicious rsync server can crash the client by sending a specially crafted file list with CF_INC_RECURSE set, causing the receiver to read 8 bytes before the allocated pointer array and dereference an invalid pointer, resulting in a deterministic SIGSEGV.

MitigationUpdate rsync to a version beyond 3.4.2 when available. Until then, avoid connecting to untrusted or unverified rsync servers, as the vulnerability is triggered by malicious server responses.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
RsyncApplication
Affected:<= 3.4.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed rsync version
    Run 'rsync --version' or 'rsync -V' to retrieve the exact version number
    Affected if Version is 3.4.2 or any prior version
  2. Determine if rsync operates as client
    Review crontabs, scripts, and running processes for rsync commands using remote server syntax (user@host::module or rsync://)
    Affected if rsync is used to pull or push data to remote servers
  3. Map rsync server connections
    Inventory all remote rsync server destinations referenced in configuration files, scripts, and automation
    Affected if connections to untrusted or unknown rsync servers exist

Environment is affected if running rsync version 3.4.2 or prior AND the rsync client connects to remote servers

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 3.4.2
Interim mitigation

Update rsync to a version beyond 3.4.2 when available. Until then, avoid connecting to untrusted or unverified rsync servers, as the vulnerability is triggered by malicious server responses.

Recommended fix Moderate confidence

rsync 3.4.3 or later stable release (check rsync.samba.org for the latest version)

  1. 1. Check the current installed rsync version by running: rsync --version
  2. 2. If the installed version is 3.4.2 or earlier, plan to upgrade to a fixed version.
  3. 3. Obtain the latest stable rsync release from the official rsync repository at rsync.samba.org or your distribution's package manager.
  4. 4. Verify that the fixed version addresses this specific vulnerability by checking the rsync release notes or changelog.
  5. 5. After upgrading, test rsync operations to ensure normal functionality.
  6. 6. If upgrading is not immediately possible, consider network-level mitigations such as restricting which rsync servers clients can connect to, to avoid connecting to untrusted malicious servers.
Caveat Standard upgrade should have minimal breaking changes; rsync protocol compatibility is generally maintained across minor versions

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Rsync Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,380
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,808.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-43620 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data