dbcve.org
Erlang\/otpApplication · Erlang

CVE-2026-55950

MEDIUM · 5.9 CVSS v3.1 Published 2026-07-02
Fix available
A fix is available. Upgrade to 11.2.12.10 / 11.6.0.3 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click Patch available 7 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Time-of-check Time-of-use (TOCTOU) race condition vulnerability in Erlang/OTP ssl (dtls_packet_demux module) allows an unauthenticated remote attacker to crash all active DTLS sessions on a listener. A DTLS server listener uses a single shared dtls_packet_demux gen_server process to route incoming UDP datagrams to the correct connection handler. When a DTLS client reconnects rapidly from the same source address and port (sending multiple ClientHello messages in quick succession), a race condition in the demux's internal gb_trees key-value store causes a {key_exists, {old, Client}} crash, terminating the demux process. Because the demux is shared across all DTLS associations on that listener, its crash immediately kills every active DTLS session, not just the attacker's. The attack is pre-authentication: the attacker only needs to send UDP datagrams containing valid ClientHello messages from the same source IP and port before the intermediate DOWN monitor message is processed by the gen_server. No credentials, no completed handshake, and no special configuration are required, and the crash can be repeated indefinitely to create a persistent denial of service for all clients of that listener. This vulnerability is associated with program file lib/ssl/src/dtls_packet_demux.erl. This issue affects OTP from OTP 25.3 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 10.9 before 11.7.3, 11.6.0.3 and 11.2.12.10.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Erlang\/otpApplication
Affected:>= 25.3, < 27.3.4.14>= 28.0, < 28.5.0.3>= 29.0, < 29.0.3
Erlang\/sslApplication
Affected:>= 10.9, < 11.2.12.10>= 11.3, < 11.6.0.3>= 11.7, < 11.7.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 11.2.12.10 / 11.6.0.3 / 11.7.3 or later
Fixed in 11.2.12.1011.6.0.311.7.3
Vendor patch github.com →
Recommended fix High confidence

OTP 29.0.3 or later (or OTP 27.3.4.14 / 28.5.0.3 for older major versions)

  1. Identify the current Erlang/OTP version in use with 'erl -eval 'erlang:display(erlang:system_info(otp_release)), halt()' -noshell'
  2. If running a version between 25.3 and 27.3.4.13, upgrade to OTP 27.3.4.14 or later
  3. If running a version between 28.0 and 28.5.0.2, upgrade to OTP 28.5.0.3 or later
  4. If running a version between 29.0 and 29.0.2, upgrade to OTP 29.0.3 or later
  5. If running OTP 27.3.4.14+, 28.5.0.3+, or 29.0.3+, verify the ssl application version matches: ssl:info() shows version 11.2.12.10+, 11.6.0.3+, or 11.7.3+ respectively
  6. After upgrade, restart any DTLS listeners to ensure the patched demux process is used
  7. Test DTLS functionality to confirm the race condition is resolved
Caveat Major OTP upgrades between major versions (e.g., 27 to 28) may have breaking changes; review the OTP migration guide for your respective version jump

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

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