CVE-2026-70455

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.

CVSS 4.0

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.6% chance of exploitation in the next 30 days; higher than 46% of CVEs (scores of 2026-10-25)

CWE

CWE-770

Published

2026-08-13

Modified

2026-10-24

Record from

the NVD, synced 2026-10-24

Affected

• samba:rsync

References

• https://github.com/RsyncProject/rsync/releases/tag/v3.5.0
• https://github.com/RsyncProject/rsync/security/advisories/GHSA-rjvj-qgqg-cvx9
• https://www.vulncheck.com/advisories/rsync-dos-via-zt-zstandard-compression-thread-exhaustion

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