Vulnerability · Published Aug 13, 2026 · Assigned by VulnCheck
CVE-2026-70455rsync 3.4.2 < 3.5.0 DoS via --zt Zstandard Compression Thread Exhaustion
High 7.5
In plain English
A high-severity resource allocation without limits in rsync from RsyncProject. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | rsync | 3.5.0-3.el10_2 | ALSA-2026:67463 |
| AlmaLinux:10 | rsync-daemon | 3.5.0-3.el10_2 | ALSA-2026:67463 |
| AlmaLinux:10 | rsync-rrsync | 3.5.0-3.el10_2 | ALSA-2026:67463 |
| Alpine:v3.21 | rsync | 3.5.0-r0 | ALPINE-CVE-2026-70455 |
| Alpine:v3.22 | rsync | 3.5.0-r0 | ALPINE-CVE-2026-70455 |
| Alpine:v3.23 | rsync | 3.5.0-r0 | ALPINE-CVE-2026-70455 |
| Alpine:v3.24 | rsync | 3.5.0-r0 | ALPINE-CVE-2026-70455 |
| Debian:12 | rsync | no fix listed | DEBIAN-CVE-2026-70455 |
| Debian:13 | rsync | 3.5.0+ds1-0+deb13u1 | DEBIAN-CVE-2026-70455 |
| Debian:14 | rsync | 3.5.0+ds1-1 | DEBIAN-CVE-2026-70455 |
| Rocky Linux:10 | rsync | 0:3.5.0-3.el10_2 | RLSA-2026:67463 |
| Ubuntu:22.04:LTS | rsync | no fix listed | UBUNTU-CVE-2026-70455 |
| Ubuntu:24.04:LTS | rsync | no fix listed | UBUNTU-CVE-2026-70455 |
| Ubuntu:26.04:LTS | rsync | no fix listed | UBUNTU-CVE-2026-70455 |
| Ubuntu:26.10 | rsync | no fix listed | UBUNTU-CVE-2026-70455 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| RsyncProject | rsync | 3.4.2 – through 3.4.4 |
Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- GitHub Security Advisory (GHSA-rjvj-qgqg-cvx9) vendor-advisory
- rsync 3.5.0 Release Notes release-notes
- https://www.vulncheck.com/advisories/rsync-dos-via-zt-zstandard-compression-thread-exhaustion third-party-advisory