CVE-2026-70455

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{"bugzilla": {"description": "rsync: rsync: Denial of Service via Zstandard compression thread exhaustion", "id": "2515406", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2515406"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-770", "details": ["rsync 3.4.2 before 3.5.0\u00a0contains 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.", "A denial-of-service flaw in rsync allows remote attackers to exhaust system memory and CPU. By sending requests using the --zt Zstandard compression alias, an attacker can bypass security directives and spawn an excessive number of worker threads."], "mitigation": {"lang": "en:us", "value": "If the rsync daemon is unused, immediately disable rsyncd.service to eliminate the attack surface. For active deployments, restrict network access (TCP 873) strictly to trusted hosts using firewall rules. Do not rely on refuse options = compress-threads for protection, as the --zt alias bypasses this configuration. Network isolation is the most effective defense."}, "name": "CVE-2026-70455", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "rsync", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "rsync", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "rsync", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "rsync", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "rsync", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "rhcos", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-08-13T14:45:11Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-70455\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-70455\nhttps://github.com/RsyncProject/rsync/releases/tag/v3.5.0\nhttps://github.com/RsyncProject/rsync/security/advisories/GHSA-rjvj-qgqg-cvx9\nhttps://www.vulncheck.com/advisories/rsync-dos-via-zt-zstandard-compression-thread-exhaustion"], "statement": "This Important rsync denial-of-service vulnerability allows remote, unauthenticated attackers to exhaust server resources. By using the --zt alias for Zstandard compression, attackers can bypass refuse options to spawn unlimited worker threads and disrupt the service. RHEL 9 and older versions are unaffected.", "threat_severity": "Important"}

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