CVE-2026-55737: Erlang Erlang/otp

High severity, CVSS 7.5. EPSS: 0.3% chance of exploitation in the next 30 days.

Signed to Unsigned Conversion Error and Out-of-bounds Write vulnerability in Erlang OTP erts allows an attacker who can supply a crafted Erlang external term format (ETF) binary to binary_to_term/1 to corrupt the BEAM heap pointer and crash the virtual machine. When decoding a LARGE_TUPLE_EXT term, the validation pass decoded_size() in erts/emulator/beam/external.c reads the 32-bit arity field as unsigned (get_uint32()), while the decode pass dec_term() reads the same field as a signed 32-bit integer (get_int32()) into an int. An arity wire value of 0x80000000 passes validation as 2147483648 but decodes as -2147483648, so the subsequent hp += n moves the heap allocation pointer backward. Neither pass enforces the runtime tuple-arity limit MAX_ARITYVAL. The result is an out-of-bounds heap write; in practice the VM detects an impossible heap size and aborts, denying service. The required padding is large when uncompressed but the compressed-ETF envelope shrinks it to a small payload on the wire. This issue affects OTP from OTP 25.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to erts from 13.0 before 17.0.4, 16.4.0.4 and 15.2.7.11.

Affected products

• Erlang Erlang/otp: from 25.0, before 27.3.4.15 (fixed in 27.3.4.15); from 28.0, before 28.5.0.4 (fixed in 28.5.0.4); from 29.0, before 29.0.4 (fixed in 29.0.4)
• Erlang Erts: from 13.0, before 15.2.7.11 (fixed in 15.2.7.11); from 16.0, before 16.4.0.4 (fixed in 16.4.0.4); from 17.0, before 17.0.4 (fixed in 17.0.4)

Published 2026-07-27. Last modified 2026-08-10.