CVE-2026-71218
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk31th percentile - higher than 31% of all known CVEs
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.
Risk Assessment
An attacker can remotely cause the iperf3 service to crash, leading to disruptions in network performance testing tools.
Recommendation
Update iperf3 to a version with a fix that limits memory allocation in the JSON_read() function.
Other vulnerabilities in iperf3
See all- CVE-2026-101283Critical
iperf3 3.20–3.21 (esnet/iperf) has a pre-auth heap buffer overflow in decrypt_rsa_message(): a 256-byte RSA buffer is BIO_read with the attacker-controlled ciphertext length (guard warns only), so an unauthenticated client overflows the heap via an oversized authtoken; fixed in 3.22
- CVE-2026-101276Critical
iperf3 version 3.21 (esnet/iperf) contains a remote, unauthenticated heap use-after-free: the server's per-test watchdog server_timer_proc() frees streams without cancelling/joining their worker threads, so a blocked worker dereferences a freed iperf_stream; fixed in 3.22.
- CVE-2026-102253High
iperf3 versions prior to 3.22 contains a denial of service vulnerability that allows unauthenticated remote attackers to crash-loop the server's UDP receive worker into an unrecoverable infinite loop by sending a single crafted control-channel parameter message followed by one 16-byte UDP datagram. Attackers can permanently pin the affected per-stream receive thread at approximately 100% CPU usage, rendering the server unusable until forcibly killed with SIGKILL, as the process does not respond to normal control-channel closure.
- CVE-2026-71217High
A flaw was found in iperf3. A remote attacker can exploit this vulnerability by sending crafted control-channel JSON with oversized numeric parameters, such as `parallel` and `len`, which are not properly validated by the server. This improper input validation can lead to excessive stream and thread creation, as well as large buffer allocations, causing resource exhaustion. Consequently, this can result in a Denial of Service (DoS) on the affected iperf3 server.
- CVE-2023-38403High
In iperf3 versions before 3.14, a vulnerability allows peers to cause an integer overflow and heap corruption via a crafted length field.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS