# CVE-2026-101276: 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.

CVE-2026-101276 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-101276, released October 5, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-101276
- Priority: Urgent
- CVSS: n/a (Critical)
- EPSS: 0.0040
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 30, 2026
- Weakness: Use After Free
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-101276

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | iperf opensuse-leap 16.0 | 3.21-160000.1.1 | [OPENSUSE-SU-2026:22090-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22090-1.md) | Nov 7, 2026 |
| Linux | iperf sles 15.7 | 3.22-150000.3.18.1 | [SUSE-SU-2026:4678-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4678-1.md) | Nov 7, 2026 |
| Linux | iperf sles 16.0 | 3.21-160000.1.1 | [SUSE-SU-2026:24234-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24234-1.md) | Nov 7, 2026 |
| Linux | iperf3 Debian 14 | 3.22-0.1 | [DEBIAN-CVE-2026-101276](https://patchblox.com/security/data/fix/linux/debian-cve-2026-101276.md) | Oct 5, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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