NVD / CVE Program· CNA EEF

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

Noroxi assessment

Priority: Monitor (action score 8/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.63% (FIRST EPSS); higher than 50.8% of all records.
Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No special conditions are required; it is repeatable.
Fixed version: erlang rebar3 1d4478f527e373de0b225951e53115450e0d9b9d, 3.27.0; hexpm hex 2.3.2, 636739f3322514e9303ca335fb630696fcbb3c95; hexpm hex_core 0.12.1, cdf726095bca85ad2549d146df1e831ae93c2b13.

Low priority for now. Upgrade to erlang rebar3 1d4478f527e373de0b225951e53115450e0d9b9d, 3.27.0; hexpm hex 2.3.2, 636739f3322514e9303ca335fb630696fcbb3c95; hexpm hex_core 0.12.1, cdf726095bca85ad2549d146df1e831ae93c2b13 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

LowCVSS 2.0 · v4.0—No exploit Fix available

Published: Feb 27, 2026
Updated: Jun 17, 2026
EPSS: 0.6% · 50th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 8 / 40 · 2.0 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.6%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · EEF: 2.0; NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
hex	hex	cpe:2.3:a:hex:hex
hex	hex core	cpe:2.3:a:hex:hex_core
erlang	rebar3	cpe:2.3:a:erlang:rebar3

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

erlang rebar33.9.1 and later · before 3.27.0
hex hex2.3.0 and later · before 2.3.2
hex hex core0.1.0 and later · before 0.12.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

erlang rebar3
- 209c02ec57c2cc3207ee0174c3af3675b8dc8f79 and later · before 1d4478f527e373de0b225951e53115450e0d9b9daffected · git
- 3.9.1 and later · before 3.27.0affected · semver
hexpm hex
- 314546ac432229518714cc8e3336e916b9da6305 and later · before 636739f3322514e9303ca335fb630696fcbb3c95affected · git
- 2.3.0 and later · before 2.3.2affected · semver
hexpm hex_core
- eb327f8edfe45507351e38cc0805aa12fa647f0b and later · before cdf726095bca85ad2549d146df1e831ae93c2b13affected · git
- 0.1.0 and later · before 0.12.1affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	rebar3	from 0	—
Debian:13	erlang-hex	from 0	—
Debian:14	erlang-hex	before 2.4.2-2	2.4.2-2
Debian:14	rebar3	before 3.27.0-1	3.27.0-1
Hex	hex_core	from 0.1.0 · before 0.12.1	0.12.1
Hex	hex_core	before 0.12.1	0.12.1

Same product

hex: all records

Other highest-scoring records for the same primary product.

CVE-2026-32148Lockfile checksums not verified in Hex allows dependency integrity bypass
35Monitor
CVE-2019-1000012Hex package manager version 0.14.0 through 0.18.2 contains a Signing oracle vulnerability in Package registry verification that can result i
35Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
erlang rebar3	1d4478f527e373de0b225951e53115450e0d9b9d	Vendor (CNA)
erlang rebar3	3.27.0	Vendor (CNA)
hexpm hex	2.3.2	Vendor (CNA)
hexpm hex	636739f3322514e9303ca335fb630696fcbb3c95	Vendor (CNA)
hexpm hex_core	0.12.1	Vendor (CNA)
hexpm hex_core	cdf726095bca85ad2549d146df1e831ae93c2b13	Vendor (CNA)
debian:erlang-hex	2.4.2-2 · Debian:14	Package registry (OSV)
debian:rebar3	3.27.0-1 · Debian:14	Package registry (OSV)
Hex:hex_core	0.12.1	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Michael Lubas / Paraxial.iofinder
Eric Meadows-Jönsson / Hex.pmremediation reviewer
Jonatan Männchen / EEFremediation developer

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

HexHackerOne · disclosure only (VDP)

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
A low-privileged account is enough.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: A
Scope: X

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:07 PM UTC

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References

cna.erlef.org/cves/CVE-2026-21619.html

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records