Vulnerability · Published Sep 30, 2026 · Assigned by Anthropic
CVE-2026-101276
Critical 9.2
In plain English
A critical-severity use-after-free in iperf3 from esnet. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 4.0)9.2Critical
Exploit odds (30 days)0.4%top 66.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
iperf3 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | iperf3 | no fix listed | DEBIAN-CVE-2026-101276 |
| Debian:14 | iperf3 | 3.22-0.1 | DEBIAN-CVE-2026-101276 |
| Ubuntu:26.04:LTS | iperf3 | no fix listed | UBUNTU-CVE-2026-101276 |
| Ubuntu:26.10 | iperf3 | no fix listed | UBUNTU-CVE-2026-101276 |
Affected products (as reported)
Weakness: CWE-416 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N