CVE-2026-105274
hex_core decompresses registry and Erlang term API responses without size limits
Published Oct 12, 2026 · updated Oct 15, 2026
## 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
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 - 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 - OSV.devPackage advisoryEEF-CVE-2026-105274
hex_core decompresses registry and Erlang term API responses without size limits
osv.dev