Medium [CVE-2026-71218] Unbounded peer-controlled allocation in iperf3 JSON_read allows unauthenticated remote memory exhaustion
This medium-severity Red Hat Linux advisory covers CVE-2026-71218 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8.
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Summary
A flaw was found in iperf3. A remote unauthenticated attacker can exploit a vulnerability in the `JSON_read()` function, which accepts a peer-controlled message length and allocates memory without an upper bound.
This allows the attacker to trigger excessive memory consumption, leading to a Denial of Service (DoS) through memory exhaustion, severe slowdown, or termination of the iperf3 service. Red Hat severity: Moderate — CVSS 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
Weakness: CWE-789. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: iperf3.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 26 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 26 days ago·verify at source
Mitigation checklist
- To mitigate this issue, restrict network access to the `iperf3` control port, ensuring it is only reachable by trusted clients. This can be achieved by configuring firewall rules to limit inbound connections to the `iperf3` service. Additionally, consider running the `iperf3` service within environments that enforce process or container memory limits to further contain potential resource exhaustion. Note that authentication alone is insufficient as the memory allocation occurs before authentication checks.
Official advisory · high-confidence parse· fetched 26 days ago·verify at source
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