CVE-2026-65634: Erlang OTP asn1 OBJECT IDENTIFIER decoder algorithmic complexity denial of service

CVE-2026-65634 · Severity: info · Published 2026-09-22

Erlang OTP's ASN.1 library contains an inefficient decoder for OBJECT IDENTIFIER values that processes crafted identifiers in quadratic time relative to their size. An attacker can send a specially crafted X.509 certificate with a malformed OID during a TLS handshake to cause a Erlang service to consume excessive CPU and become unresponsive, without requiring authentication or valid trust chain verification. This affects any Erlang application using TLS, including web servers and services that accept client certificates.

Technologies: Erlang OTP. Vendors: Erlang.

Quick answers

Is CVE-2026-65634 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-65634 being exploited in the wild.
How severe is CVE-2026-65634?
Informational severity, published 22 September 2026.
Which products and versions are affected?
Erlang Asn1 3.0 before 5.3.4.3, 5.4.x before 5.4.3.1, 5.5.x before 5.5.2; Erlang OTP 17.0 before 27.3.4.18, 28.x before 28.5.0.7, 29.x before 29.1.1.
Is there a fix for CVE-2026-65634?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-65634 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-65634?
Check whether you run Erlang Asn1 or Erlang OTP at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The BER/PER/JER OID decoders in asn1rtt_ber:dec_subidentifiers/3, asn1rtt_per_common:dec_subidentifiers/3, and asn1rtt_jer:json2oid/1 accumulate base-128 encoded subidentifiers using unbounded integer arithmetic with O(n²) algorithmic complexity per continuation byte. The vulnerability is triggered during X.509 certificate parsing via public_key:pkix_decode_cert/2, which executes before signature or trust verification. A ~262 KB crafted OID can consume ~13 seconds of CPU on typical hardware, enabling remote DoS against TLS endpoints.

Affected products

  • Erlang OTP 17.0 before 27.3.4.18, 28.x before 28.5.0.7, 29.x before 29.1.1
  • Erlang asn1 3.0 before 5.3.4.3, 5.4.x before 5.4.3.1, 5.5.x before 5.5.2

Timeline

  • 2026-09-22: disclosed

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