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CVE-2026-21619: Unsafe Deserialization of Erlang Terms in hex_core

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-27 · updated 2026-06-17
• Weakness: CWE-400

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.

Affected products

• erlang rebar3: from 3.9.1 before 3.27.0 — fixed in 3.27.0
• hexpm hex: from 2.3.0 before 2.3.2 — fixed in 2.3.2
• hexpm hex_core: from 0.1.0 before 0.12.1 — fixed in 0.12.1

How to fix

Upgrade to a fixed version: erlang rebar3 3.27.0; hexpm hex 2.3.2; hexpm hex_core 0.12.1. Check the vendor advisory for mitigations.

References

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

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