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Vulnerability · Published Sep 22, 2026 · Assigned by EEF

CVE-2026-65634Superlinear CPU denial of service in Erlang/OTP ASN.1 OBJECT IDENTIFIER decoder

High 8.2

In plain English

A high-severity security flaw in OTP from Erlang. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.2High
Exploit odds (30 days)0.3%top 81.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12erlangno fix listedDEBIAN-CVE-2026-65634
Debian:13erlang1:27.3.4.1+dfsg-1+deb13u4DEBIAN-CVE-2026-65634
Debian:14erlang1:29.1.1+dfsg-1DEBIAN-CVE-2026-65634
Ubuntu:22.04:LTSerlang1:24.2.1+dfsg-1ubuntu0.8UBUNTU-CVE-2026-65634
Ubuntu:22.04:LTSerlang1:24.2.1+dfsg-1ubuntu0.8USN-8901-1
Ubuntu:24.04:LTSerlang1:25.3.2.8+dfsg-1ubuntu4.8USN-8901-1
Ubuntu:24.04:LTSerlang1:25.3.2.8+dfsg-1ubuntu4.8UBUNTU-CVE-2026-65634
Ubuntu:26.04:LTSerlang1:27.3.4.6+dfsg-1ubuntu0.2USN-8901-1
Ubuntu:26.04:LTSerlang1:27.3.4.6+dfsg-1ubuntu0.2UBUNTU-CVE-2026-65634
Ubuntu:26.10erlangno fix listedUBUNTU-CVE-2026-65634

Affected products (as reported)

VendorProductVersions
Erlang OTP 17.0 – before *
Erlang OTP 3.0 – before *
Erlang OTP 84adefa331c4159d432d22840663c38f155cd4c1 – before 0fe2c02fdc06fab1c63be9db1a7456993d20f838

Weakness: CWE-407 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References