# CVE-2026-55737

## Summary

- **CVE ID:** CVE-2026-55737
- **Severity:** MEDIUM
- **CVSS Score:** 5.1 (CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N)
- **CWE:** CWE-195, CWE-787
- **Published:** Jul 27, 2026
- **Last Modified:** Jul 28, 2026

## 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 27.3.4.15, 28.5.0.4, and 29.0.4 corresponding to erts from 13.0 before 15.2.7.11, 16.4.0.4, and 17.0.4.

## Affected Products

- Erlang — OTP (13.0)
- Erlang — OTP (25.0)
- Erlang — OTP (ebcbb97b4ec223464cac3d94375739a248ddef6e)

## References

- [CNA](https://github.com/erlang/otp/security/advisories/GHSA-446w-268v-9462)
- [CNA](https://cna.erlef.org/cves/CVE-2026-55737.html)
- [CNA](https://osv.dev/vulnerability/EEF-CVE-2026-55737)
- [CNA](https://www.erlang.org/doc/system/versions.html#order-of-versions)
- [CNA](https://github.com/erlang/otp/commit/c5210b42a9d3d96f3d25601942ce8122be0f3761)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.29%
- **EPSS Percentile:** 21.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-12._