CVE-2026-21619: Hex core Hex_core Has Unsafe Deserialization Of Vulnerability

LOW
Advisory Identifier: GHSA-hx9w-f2w9-9g96
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CWE-400
Published
Advisory Summary

CVE-2026-21619 is a LOW hex_core has unsafe deserialization of vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Hex core libraries in the Hex ecosystem. The issue involves hex_core has unsafe deserialization of erlang terms. Remediation is available by upgrading affected packages to version 0.12.1.

CVE-2026-21619 at a Glance

CVE Identifier CVE-2026-21619
GHSA Identifier GHSA-hx9w-f2w9-9g96
Severity LOW
CVSS v3.1 Base Score N/A
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Hex core
Package Ecosystem Hex
Published Date
Last Updated

How to Fix CVE-2026-21619

To remediate this vulnerability, upgrade all affected Hex core dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

hex_core fixed: 0.12.1 
Upgrade hex_core to 0.12.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for hex_core

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-21619, inspect your project dependencies for Hex core:

inspect dependencies for hex_core

Analyze the terminal output to locate any version of Hex core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.12.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Hex core, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact The Hex client (`hex_core`) deserializes Erlang terms received from the Hex API using `binary_to_term/1` without sufficient restrictions. If an attacker can control the HTTP response body returned by the Hex API, this allows denial-of-service attacks such as **atom table exhaustion**, leading to a VM crash. No released versions are known to allow remote code execution. ### Patches * https://github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13 * https://github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95 * https://github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d ### Workarounds Ensure that the Hex API URL (`HEX_API_URL`) points only to trusted endpoints. There is no client-side workaround that fully mitigates this issue without applying the patch. ### Resources * hex_core Module: https://github.com/hexpm/hex_core/blob/main/src/hex_api.erl * Hex Vendored Module: https://github.com/hexpm/hex/blob/main/src/mix_hex_api.erl * Rebar3 Vendored Module: https://github.com/erlang/rebar3/blob/main/apps/rebar/src/vendored/r3_hex_api.erl * hex_core Patch: https://github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13 * Hex Vendored Patch: https://github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95 * Rebar3 Vendored Patch: https://github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d

CVE-2026-21619 Affected Hex core Versions

1 component(s)
Fixed Versions:
0.12.1
Product / Package Ecosystem Affected Versions Fixed Version
hex_core
 Hex
< 0.12.1
0.12.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/hexpm/hex_core/security/advisories/GHSA-hx9w-f2w9-9g96
NVD — CVE-2026-21619 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-21619
Security Fix Commit FIX COMMIT
https://github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d
Security Fix Commit FIX COMMIT
https://github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95
Security Fix Commit FIX COMMIT
https://github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13
cna.erlef.org/cves/cve-2026-21619... WEB
https://cna.erlef.org/cves/CVE-2026-21619.html
Hex core Source Repository REPOSITORY
https://github.com/hexpm/hex_core
osv.dev/vulnerability/eef-c... WEB
https://osv.dev/vulnerability/EEF-CVE-2026-21619

Frequently Asked Questions

What is CVE-2026-21619?
CVE-2026-21619 is a security vulnerability in Hex core involving hex_core has Unsafe Deserialization of Erlang Terms under CWE-400: Uncontrolled Resource Consumption.
Which Hex core versions are affected?
Affected versions include releases prior to 0.12.1 across affected packages: hex_core.
What version fixes CVE-2026-21619?
Upgrading to 0.12.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hex_core affected?
Yes, hex_core is affected in releases prior to 0.12.1. Upgrade your dependency to 0.12.1 or later.
What CWE is associated with CVE-2026-21619?
CVE-2026-21619 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check Hex dependencies for CVE-2026-21619?
Run the dependency tree command: 'inspect dependencies for hex_core'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-hx9w-f2w9-9g96",
  "modified" : "2026-04-06T23:15:53Z",
  "published" : "2026-03-01T01:25:35Z",
  "aliases" : [ "CVE-2026-21619" ],
  "summary" : "hex_core has Unsafe Deserialization of Erlang Terms",
  "details" : "### Impact\n\nThe Hex client (`hex_core`) deserializes Erlang terms received from the Hex API using `binary_to_term/1` without sufficient restrictions.\n\nIf an attacker can control the HTTP response body returned by the Hex API, this allows denial-of-service attacks such as **atom table exhaustion**, leading to a VM crash. No released versions are known to allow remote code execution.\n\n### Patches\n\n* https://github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13\n* https://github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95\n* https://github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d\n\n### Workarounds\n\nEnsure that the Hex API URL (`HEX_API_URL`) points only to trusted endpoints. There is no client-side workaround that fully mitigates this issue without applying the patch.\n\n### Resources\n\n* hex_core Module: https://github.com/hexpm/hex_core/blob/main/src/hex_api.erl\n* Hex Vendored Module: https://github.com/hexpm/hex/blob/main/src/mix_hex_api.erl\n* Rebar3 Vendored Module: https://github.com/erlang/rebar3/blob/main/apps/rebar/src/vendored/r3_hex_api.erl\n* hex_core Patch: https://github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13\n* Hex Vendored Patch: https://github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95\n* Rebar3 Vendored Patch: https://github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "hex_core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.12.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/hexpm/hex_core/security/advisories/GHSA-hx9w-f2w9-9g96"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-21619"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-21619.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/hexpm/hex_core"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-21619"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-01T01:25:35Z",
    "nvd_published_at" : "2026-02-27T18:16:11Z"
  }
}