Medium [CVE-2026-70453] Denial of Service via Algorithmic Complexity
This medium-severity Red Hat Linux advisory covers CVE-2026-70453 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 6.
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Summary
rsync before 3.5.0 contains an algorithmic complexity vulnerability in the hash_search() function that allows a remote attacker to cause a denial of service by delivering a carefully constructed file list.
A sender can exploit the quadratic-time worst-case behavior in hash lookups to exhaust receiver CPU resources with a modest number of crafted entries, causing a sustained denial of service. A flaw was found in rsync.
By sending a specially crafted file list, an attacker can exhaust the receiver's CPU resources, leading to service unavailability. This is particularly relevant in Red Hat environments where rsync is used for remote file synchronization and may be exposed to untrusted networks.
Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H). Weakness: CWE-770.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat OpenShift Container Platform 4. Red Hat fixing advisory: RHSA-2026:67463, RHSA-2026:67462.
Affected products named by the advisory: Red Hat package: rsync.
- < 3.5.0
Official advisory · high-confidence parse· fetched 17 days ago·verify at source
- 3.5.0
- rsync-0:3.5.0-3.el10_2
- rsync-0:3.2.7-1.el9_8
- RHSA-2026:67463
- RHSA-2026:67462
Official advisory · high-confidence parse· fetched 17 days ago·verify at source
Mitigation checklist
- Disable unused rsyncd services (systemctl disable --now rsyncd), or restrict daemon access to trusted clients via hosts allow and firewall rules. Avoid synchronizing with untrusted senders or pushing to untrusted receivers and upload modules to prevent processing malicious file lists. To contain potential Denial of Service, enforce CPU resource limits on rsync processes using systemd cgroups or ulimit -t to prevent a quadratic search walk from starving the host.
Official advisory · high-confidence parse· fetched 17 days ago·verify at source
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