CVE-2026-105274
hex_core decompresses registry and Erlang term API responses without size limits
Published Oct 12, 2026 · corrected/updated Oct 15, 2026 · evidence confidence high
## Summary Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in hexpm hex_core allows an untrusted repository mirror, or a server answering hex_core's API requests, to exhaust the memory of the Erlang VM running hex_core. The same code is vendored in Hex ( , ) and rebar3 ( , ). , , and decompress the registry response with and decode the signed envelope before verifying its signature. A mirror doesn't have the repository's private key, but it chooses the compressed bytes, so a small response decompresses into an envelope of any size before the signature check rejects it. decodes responses with the content type through , which calls . The option prevents atom creation, but it accepts compressed terms and doesn't limit the size of the decoded term, and the check that rejects functions and ports runs after the term has been built. The fix for CVE-2026-21619 added the option and that check without bounding the decoded size. This issue affects rebar3: from 3.9.1 before 3.27.3; hex: from 2.1.0 before 2.5.2; hex_core: from 0.1.0 before 0.20.0. ## Details 1. , used by , , and , calls on the whole response body with no output limit. 2. then calls , which decodes the protobuf envelope, copying its payload and signature, before checking the signature. 3. passes every response whose content type contains to . 4. calls , which decompresses compressed terms and builds the whole term, and only then walks it to reject functions and ports. ## Proof of concept 1. Point a repository at a loopback mirror (in Hex, ) that answers with a 65,268-byte gzip stream decompressing to a 67,108,872-byte signed envelope with a 64 MiB payload and a one-byte signature. 2. , which calls the vendored , returns after allocating the envelope. Peak RSS was 234 MiB, against 96 MiB for a 1,030-byte invalid envelope. 3. Answer an API request with and 8,178 bytes of compressed Erlang term format encoding a list of 4,194,304 elements. accepts the decoded term, and BEAM memory rise
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-105274 is a low public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: hex_core (0.1.0 → 0.20.0). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 2.1, EPSS 0.4%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-409. Sources contributing to this record: cve_org, epss, github, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Oct 12, 2026 · GitHub Advisory Database
Detected
## Summary Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in hexpm hex_core allows an untrusted repository mirror, or a server answering hex_core's API requests, to exhaust the memory of the Erlang VM running hex_core. The same code is vendored in Hex ( , ) and rebar3 ( , ). , , and decompress the registry response with and decode the signed envelope before verifyin
Oct 12, 2026 · GitHub Advisory Database
Fix available
hex_core fixed in 0.20.0
Oct 12, 2026 · GitHub Advisory Database
Fix available
hex_core fixed in 0.20.0
Oct 12, 2026 · GitHub Advisory Database
Updated
## Summary Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in hexpm hex_core allows an untrusted repository mirror, or a server answering hex_core's API requests, to exhaust the memory of the Erlang VM running hex_core. The same code is vendored in Hex ( , ) and rebar3 ( , ). , , and decompress the registry response with and decode the signed envelope before verifyin
Oct 15, 2026 · NIST NVD
Updated
Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in hexpm hex_core allows an untrusted repository mirror, or a server answering hex_core's API requests, to exhaust the memory of the Erlang VM running hex_core. The same code is vendored in Hex (mix_hex_repo, mix_hex_api) and rebar3 (r3_hex_repo, r3_hex_api). hex_repo:get_names/1, hex_repo:get_versions/1, hex_repo:get_p
Affected
- Hex hex_core0.1.0 → 0.20.0
Sources
- CVE.orgVulnerability recordCVE-2026-105274
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-105274
30-day exploitation probability 0.4%
first.org - GitHub Advisory DatabasePackage advisoryGHSA-7c4r-cgf9-9jmq
GitHub Advisory Database record mirrored by OSV.
github.com - NIST NVDVulnerability recordCVE-2026-105274
Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in hexpm hex_core allows an untrusted repository mirror, or a server answering hex_core's API requests, to exhaust the memory of the Erlang VM running hex_core. The same code is vendored in Hex (mix_he
nvd.nist.gov - OpenSSF OSV / OSV ScannerPackage advisoryEEF-CVE-2026-105274
hex_core decompresses registry and Erlang term API responses without size limits
osv.dev