CVE-2026-55950Network attack vector

Pre-authentication DTLS listener crash via demultiplexer race

Published Jul 2, 2026 · Updated Jul 2, 2026

TOCTOU race condition in Erlang/OTP ssl allows remote attackers to crash every active DTLS session on a listener via crafted ClientHello traffic. The shared dtls_packet_demux gen_server inserts a replacement connection into gb_trees before the prior client's DOWN monitor is processed, triggering a key_exists exception. Any UDP-based ssl:listen/2 DTLS listener reachable before authentication is exposed, and repeated reconnects from one source address and port interrupt service for all clients.

CVSS severity8.7
High
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

TOCTOU race condition in Erlang/OTP ssl allows remote attackers to crash every active DTLS session on a listener via crafted ClientHello traffic. The shared dtls_packet_demux gen_server inserts a replacement connection into gb_trees before the prior client's DOWN monitor is processed, triggering a key_exists exception. Any UDP-based ssl:listen/2 DTLS listener reachable before authentication is exposed, and repeated reconnects from one source address and port interrupt service for all clients.

The record

CVE
CVE-2026-55950
Published
Jul 2, 2026
Updated
Jul 2, 2026
Vendor
Erlang
Product
Erlang/OTP
Classifications
CWE-367, CAPEC-29, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.9 <* changes=[{"at":"11.7.3","status":"unaffected"},{"at":"11.6.0.3","status":"unaffected"},{"at":"11.2.12.10","status":"unaffected"}]
  2. Affected versionversion=25.3 <* changes=[{"at":"29.0.3","status":"unaffected"},{"at":"28.5.0.3","status":"unaffected"},{"at":"27.3.4.14","status":"unaffected"}]
  3. Affected versionversion=44dcb4c3d900777493ce2a6129f451aa475811f9 <e44d2bf01c4473ef2ea7f09e3523cf96de6e4a04

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Erlang · Erlang/OTPversion=10.9 <* changes=[{"at":"11.7.3","status":"unaffected"},{"at":"11.6.0.3","status":"unaffected"},{"at":"11.2.12.10","status":"unaffected"}]; version=25.3 <* changes=[{"at":"29.0.3","status":"unaffected"},{"at":"28.5.0.3","status":"unaffected"},{"at":"27.3.4.14","status":"unaffected"}]; version=44dcb4c3d900777493ce2a6129f451aa475811f9 <e44d2bf01c4473ef2ea7f09e3523cf96de6e4a04

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7Erlang Ecosystem FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
CAPEC-29Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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