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Review reviewHigh

CVE-2026-55950

Erlang OTP, erlang/otp, erlang/ssl

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, te...

CVSS
8.7
EPSS
0.38%
30.8% percentile
CISA KEV
Not listed
Published
2026.07.03
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.38%
Technical severityCVSS 8.7

Vulnerability overview

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, te...

Affected product and versions

Product
Erlang OTP, erlang/otp, erlang/ssl
Affected versions
>= 10.9, >= 25.3, >= 44dcb4c3d900777493ce2a6129f451aa475811f9 < e44d2bf01c4473ef2ea7f09e3523cf96de6e4a04, >= 25.3 < 27.3.4.14, >= 28.0 < 28.5.0.3, >= 29.0 < 29.0.3, >= 10.9 < 11.2.12.10, >= 11.3 < 11.6.0.3, >= 11.7 < 11.7.3
Fixed versions
27.3.4.14, 28.5.0.3, 29.0.3, 11.2.12.10, 11.6.0.3, 11.7.3

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Erlang OTP, erlang/otp, erlang/ssl and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CWE
CWE-367