CVE-2026-21619 — Unsafe Deserialization of Erlang Terms in hex_core
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.6% (30-day exploitation probability)+7
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — github.com (NIST National Vulnerability Database)
- Documented patch — github.com (NIST National Vulnerability Database)
- Documented patch — github.com (NIST National Vulnerability Database)
- Documented mitigation — github.com (NIST National Vulnerability Database)
- Erlang Hex Core: fixed in version 0.12.1 — github.com (GitHub Security Advisories)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Erlang Rebar3, Hex Hex, Hex Hex Core…).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Erlang | Rebar3 | ≥ 3.9.1 and < 3.27.0 | Vulnerable | NIST National Vulnerability Database |
| Erlang | Rebar3 | ≥ 209c02ec57c2cc3207ee0174c3af3675b8dc8f79 and < 1d4478f527e373de0b225951e53115450e0d9b9d≥ 3.9.1 and < 3.27.0 | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Hex | Hex | ≥ 2.3.0 and < 2.3.2 | Vulnerable | NIST National Vulnerability Database |
| Hex | Hex Core | ≥ 0.1.0 and < 0.12.1 | Vulnerable | NIST National Vulnerability Database |
| Hexpm | Hex | ≥ 314546ac432229518714cc8e3336e916b9da6305 and < 636739f3322514e9303ca335fb630696fcbb3c95≥ 2.3.0 and < 2.3.2 | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Hexpm | Hex Core | ≥ eb327f8edfe45507351e38cc0805aa12fa647f0b and < cdf726095bca85ad2549d146df1e831ae93c2b13≥ 0.1.0 and < 0.12.1 | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Erlang | Hex Core | < 0.12.1 | Vulnerable | GitHub Security Advisories |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 2.0 | CVSS 4.0 | Low | — | — | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db via NIST National Vulnerability Database |
| 2.0 | CVSS 4.0 | Low | — | — | EEF via CVE Program (cve.org) e CISA ADP |
| 7.5 | CVSS 3.1 | High | 3.9 | 3.6 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.60%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Track CPU/memory spikes and availability drops correlated with request patterns.
Timeline
What happened to this CVE, newest first.
- 2026
- Fix documented
- Affected products added · erlang/hex core
- Affected products added · hexpm/hex core, hexpm/hex, erlang/rebar3
- SSVC assessment updated
- Record published
- Fix documented
- CVSS changed · 7.5
- Source status changed · → Modified
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 15, 2026 – Oct 15, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
8 on the record
- github.com/hexpm/hex_core/security/advisories/GHSA-hx9w-f2w9-9g96
- github.com/hexpm/hex/commit/636739f3322514e9303ca335fb630696fcbb3c95
- github.com/erlang/rebar3/commit/1d4478f527e373de0b225951e53115450e0d9b9d
- github.com/hexpm/hex_core/commit/cdf726095bca85ad2549d146df1e831ae93c2b13
- github.com/advisories/GHSA-hx9w-f2w9-9g96
- osv.dev/vulnerability/EEF-CVE-2026-21619
- cna.erlef.org/cves/CVE-2026-21619.html
- nvd.nist.gov/vuln/detail/CVE-2026-21619
Elsewhere on this site
Related CVEs (same products)
- Medium CVE-2026-96596 erl_tar:extract/2 loops forever on a GNU sparse member with a trailing hole 1d
- Low CVE-2026-105274 hex_core decompresses registry and Erlang term API responses without size limits 3d
- High CVE-2026-96612 Path traversal in Hex via unvalidated dependency app names 3d
- Low CVE-2026-96618 Hex exhausts memory and disk on oversized or compressed responses from an untrusted mirror 3d
- Low CVE-2026-81856 Terminal escape sequence injection in Hex via unneutralized server-supplied output 3d
- Medium CVE-2026-105280 Hex writes unverified package tarballs to standard output in mix hex.package fetch 3d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-21619 is "Unsafe Deserialization of Erlang Terms in hex_core", rated High. It affects Rebar3 (Erlang); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.60% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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