CVE-2026-55737: erlang erlang\/otp Signed to Unsigned Conversion Error

Vulnerability summary

CVE-2026-55737 is a high (CVSS 7.5) Signed to Unsigned Conversion Error vulnerability in erlang erlang\/otp. EPSS estimates a 0.29% chance of exploitation in the next 30 days, higher than 19.9% of scored vulnerabilities.

Timeline

1. 27-07-2026
   PublishedVulnerability first disclosed.
2. 28-07-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-195Signed to Unsigned Conversion ErrorThe product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.