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Erlang security advisory (AV26-948)

MediumCanadian Centre for Cyber Security · Canadian Centre for Cyber Security·

At a glance

Severity
Medium
Used in attacks
Not on CISA’s list
Flaws named
CVE-2026-65634CVE-2026-89422
Vendors and products
GitHub
Reported by
1 outlet

As of September 22, 2026, Erlang is affected by vulnerabilities in the following product:

  • OTP
    • 17.0 Prior to 27.3.4.18
    • 21b8a1b Prior to afec515, 98c66c8 and fd1d9d0
    • 22.2 Prior to 27.3.4.18, 28.5.0.7 and 29.1.1
    • 4.1.1 Prior to 5.2.11.13, 5.5.2.6 and 6.0.6
    • 9.5 Prior to 11.2.12.13, 11.6.0.6 and 11.7.7
    • Versions Prior to 84adefa

The Cyber Centre encourages users and administrators to review the provided web links and apply any necessary updates as they become available.

Reproduced in full under licence from Canadian Centre for Cyber Security. © Canadian Centre for Cyber Security. Written by Canadian Centre for Cyber Security.

Read at cyber.gc.ca ↗Official Source

Vulnerabilities referenced

  • CVE-2026-65634Not scored yet

    Product not named yet

    Inefficient algorithmic complexity in the Erlang/OTP asn1 OBJECT IDENTIFIER decoder allows a remote unauthenticated attacker to cause denial of service by sending a crafted OID during the TLS handshake. The BER OID decoder asn1rtt_ber:dec_subidentifiers/3 in lib/asn1/src/asn1rtt_ber.erl and the equivalent PER helper asn1rtt_per_common:dec_subidentifiers/3 in lib/asn1/src/asn1rtt_per_common.erl accumulate a base-128 subidentifier into an unbounded integer using (Av bsl 7) + H per continuation byte. Each shift and addition on the growing accumulator is linear in the number of bits already accumulated, giving quadratic total work in the size of a single subidentifier. The JER helper asn1rtt_jer:json2oid/1 in lib/asn1/src/asn1rtt_jer.erl exhibits the same class of unbounded-integer parsing when decoding a dot-separated OID from JSON. A DER-encoded OBJECT IDENTIFIER with one very large arc (approximately 262 KB of continuation bytes) consumes roughly 13 seconds of CPU on typical hardware. The vulnerable decoder is generated into every ASN.1 module that contains an OBJECT IDENTIFIER, including OTP-PUB-KEY which is reached during X.509 certificate parsing via public_key:pkix_decode_cert/2. This decoder runs before any signature or trust chain verification, so any Erlang service that parses peer TLS certificates is exposed: the default for TLS clients (which always parse the server certificate) and for mutual-TLS servers (which parse client certificates). This vulnerability is associated with program files lib/asn1/src/asn1rtt_ber.erl, lib/asn1/src/asn1rtt_per_common.erl and lib/asn1/src/asn1rtt_jer.erl and program routines asn1rtt_ber:dec_subidentifiers/3, asn1rtt_per_common:dec_subidentifiers/3 and asn1rtt_jer:json2oid/1. This issue affects OTP from OTP 17.0 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1, corresponding to asn1 from 3.0 before 5.3.4.3, 5.4.3.1, and 5.5.2. Whether OTP before OTP 17.0, corresponding to asn1 before 3.0, is affected is unknown.

    Full record →
  • CVE-2026-89422Not scored yet

    Product not named yet

    Key Exchange without Entity Authentication vulnerability in Erlang/OTP ssl allows a peer that answers a TLS 1.3 client connection to impersonate the intended server. A pre_shared_key extension in the ServerHello that the client never offered causes the client to complete the handshake without validating the server's certificate, so ssl:connect returns {ok, Socket} against a peer holding no certificate, no private key and no prior session. tls_client_connection_1_3:handle_server_hello/2 passes the received extension to tls_gen_connection_1_3:handle_resumption/2, which sets resumption = true on its mere presence without checking that the client offered a PSK. tls_handshake_1_3:get_pre_shared_key/4 meanwhile falls back to the all-zero "no PSK" value and keys the handshake with the ordinary non-PSK schedule, so the attacker's own ephemeral key suffices. The resumption flag then routes maybe_resumption/1 straight to wait_finished, skipping the certificate-handling states, so certificate path validation, verify_fun, hostname verification, partial_chain, CRL checking and OCSP stapling are all bypassed. The default client configuration is affected; clients restricted to TLS 1.2 are not. This issue affects OTP from OTP 22.2 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1, corresponding to ssl from 9.5 before 11.2.12.13, 11.6.0.6, and 11.7.7.

    Full record →

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Coverage

One outlet has carried this so far.

  1. Canadian Centre for Cyber Security ↗Official SourceFirst reported

    2026-09-22 15:30 UTC

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