CVE-2026-55950: DTLS listener crash via race condition in dtls_packet_demux causes denial of service for all sessions
CVE-2026-55950 is a vulnerability in DTLS listener crash via race condition in dtls_packet_demux causes denial of service for all sessions, rated Important by Microsoft, with a CVSS 3.1 base score of 5.9 (Medium). An attacker can exploit it remotely over the network, without any privileges and without user interaction. Microsoft has not reported exploitation in the wild. The EPSS model estimates a 0.40% probability of exploitation activity in the next 30 days, higher than 35% of all scored vulnerabilities. Microsoft released the fix on 14 August 2026, outside Patch Tuesday. It affects 1 product in 1 product family (Open Source Software).
Key facts
- CVE ID
- CVE-2026-55950
- Severity
- Medium CVSS 5.9
- Microsoft severity
- Important
- Exploited in the wild
- No
- Publicly disclosed
- No
- Weakness
- CWE-367
- EPSS
- 0.40% (percentile 35%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- July 2026 Patch Tuesday
- Product families
- Open Source Software
CVSS score and vector
Microsoft scores CVE-2026-55950 at 5.9 (temporal 5.9) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | High |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | None |
| Integrity impact | None |
| Availability impact | High |
Affected products (1)
Open Source Software
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| azl3 erlang 26.2.5.21-4 on Azure Linux 3.0 | CBL-Mariner Releases | Security Update | 26.2.5.21-5 | No |
NIST NVD data
- NVD status
- Modified
- NVD CVSS
- 5.9 (MEDIUM)
- NVD weakness
- CWE-367
- Published to NVD
- NVD last modified
Affected configurations (CPE)
| Product | Vulnerable versions |
|---|---|
| erlang\/otp | from 25.3, before 27.3.4.14 |
| erlang\/otp | from 28.0, before 28.5.0.3 |
| erlang\/otp | from 29.0, before 29.0.3 |
| erlang\/ssl | from 10.9, before 11.2.12.10 |
| erlang\/ssl | from 11.3, before 11.6.0.3 |
| erlang\/ssl | from 11.7, before 11.7.3 |
References
- https://cna.erlef.org/cves/CVE-2026-55950.html (Vendor Advisory)
- https://github.com/erlang/otp/commit/44dcb4c3d900777493ce2a6129f451aa475811f9
- https://github.com/erlang/otp/commit/e44d2bf01c4473ef2ea7f09e3523cf96de6e4a04 (Patch)
- https://github.com/erlang/otp/security/advisories/GHSA-hwfc-5hf4-gvr3 (Vendor Advisory)
- https://osv.dev/vulnerability/EEF-CVE-2026-55950 (Third Party Advisory)
- https://www.erlang.org/doc/system/versions.html#order-of-versions (Release Notes)
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. | |
| 2.0 | Information published. |