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CVE-2026-70455: rsync 3.4.2 before 3.5.0 contains a denial of service vulnerability that allows a remote sender to exhaust sys

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HIGH 7.5REMOTEUPGRADE

CVE-2026-70455 is a high-severity flaw (CVSS 7.5) affecting rsync. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

rsync 3.4.2 before 3.5.0 contains a denial of service vulnerability that allows a remote sender to exhaust system resources by specifying the --zt short alias for --compress-threads, which bypasses the refuse options directive's string matching on long option names. Attackers can specify --zt=N with a large value to spawn an unbounded number of Zstandard worker threads on the receiver, exhausting available thread and memory resources.

Why this priority

  • High severity
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score7.5 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance0.6% (top 54%)
CISA exploited listNo
WeaknessCWE-770
Published2026-08-13
Last modified2026-10-23
Publisher (CNA): VulnCheck · Vendor: samba

Am I affected?

Timeline

samba rsync UPGRADE
Affected: >= 3.4.2 and < 3.5.0
Fixed in: 3.5.0
Safe to downgrade to: a release before 3.4.2
1. Check installed version
apt-cache policy rsync || rpm -q rsync || rsync --version
2. UPGRADE to 3.5.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade rsync
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade rsync
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 3.4.2 (Debian / Ubuntu)
apt-cache madison rsync sudo apt install rsync=<VERSION_BEFORE_3.4.2> sudo apt-mark hold rsync
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list rsync sudo dnf downgrade rsync-<VERSION_BEFORE_3.4.2> sudo dnf versionlock add rsync
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · kwin-zones · FIXED · 1.0.13-1.fc46 · FEDORA-2026-95888f332b · source
sudo dnf upgrade --advisory=FEDORA-2026-95888f332b
Fedora ELN · nginx-mod-brotli · FIXED · 1.0.0~rc-16.eln159 · FEDORA-2026-501a6a8273 · source
sudo dnf upgrade --advisory=FEDORA-2026-501a6a8273
Debian 12 · rsync · NO FIX YET
Debian 13 · rsync · FIXED · 3.5.0+ds1-0+deb13u1
sudo apt update && sudo apt install --only-upgrade rsync dpkg --compare-versions "$(dpkg-query -W -f='${Version}' rsync)" ge "3.5.0+ds1-0+deb13u1" && echo PATCHED || echo STILL-VULNERABLE
RHEL 10 · rsync · FIXED · rsync-3.5.0-3.el10_2
sudo dnf upgrade --advisory=RHSA-2026:67463 rpm -q rsync
RHEL 6 · rsync · NOT AFFECTED
RHEL 7 · rsync · NOT AFFECTED
RHEL 8 · rsync · NOT AFFECTED
RHEL 9 · rsync · NOT AFFECTED
Alpine 3.21 · rsync · FIXED · rsync-3.5.0-r0
apk add --upgrade rsync apk info -v rsync
Alpine 3.22 · rsync · FIXED · rsync-3.5.0-r0
apk add --upgrade rsync apk info -v rsync
Alpine 3.23 · rsync · FIXED · rsync-3.5.0-r0
apk add --upgrade rsync apk info -v rsync
Alpine 3.24 · rsync · FIXED · rsync-3.5.0-r0
apk add --upgrade rsync apk info -v rsync
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

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References

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