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lowDenial of Servicepublic exploit

CVE-2026-96618

CVE-2026-96618 — Hex exhausts memory and disk on oversized or compressed responses from an untrusted mirror

Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in hexpm hex allows an untrusted package mirror to exhaust the memory or disk space of the machine running mix deps.get, mix deps.update, mix hex.package fetch or mix hex.docs fetch. Hex treats a mirror configured with HEX_MIRROR_URL, HEX_MIRROR or mirror_url as untrusted: it doesn't send credentials to it, and it checks registry signatures and package checksums that the mirror can't forge. Several response paths consume memory or disk in proportion to what the mirror sends before any of those checks run. Hex.HTTP.request/5 reads the whole response body into memory and decompresses it with :zlib.gunzip/1 whenever the response's Content-Encoding contains gzip, with no limit on the compressed or decompressed size. Hex doesn't ask for compressed responses, so the server decides whether this step runs. It applies to registry, package, docs and API responses. Package tarballs have no download size limit. Hex 2.5.1 holds the whole tarball in memory and writes it to the cache, and the development branch streams it to a temporary file; the 16 MiB tarball limit is checked only when the file is unpacked. The tarball is then unpacked, into deps/<app> in 2.5.1 and into a staging directory on the development branch, before its checksums are compared with the registry. mix hex.docs fetch, and mix hex.docs offline when docs are missing, write the docs tarball to disk and extract it with :mix_hex_erl_tar.extract/2 without the 16 MiB compressed and 128 MiB decompressed limits that mix_hex_tarball:unpack_docs/3 applies. The signed registry doesn't cover docs tarballs, so nothing checks them. Registry responses are also decompressed before their signature is checked, in hex_core code that Hex vendors; that part is tracked in https://github.com/hexpm/hex_core/security/advisories/GHSA-7c4r-cgf9-9jmq. This issue affects hex: from 0.11.2 before 2.5.2.

Published Updated Sources: NVD, hexpm (CNA), GitHub, Red Hat (VEX), SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Exploit code

public exploit, none observed

EPSS

0%

ahead of 0% of scored CVEs

Affects

hexpm

2 products listed

CVSS base

2.1

low · 2 sources

Remediation

The vendor's own words where we have them.

Upgrade Hex to 2.5.2 or later, for example with mix local.hex. Hex then stops downloading a registry file, package, docs tarball or other file from a repository or mirror once it's larger than 16 MiB, including after decompressing a gzip-encoded response, and checks packages against the registry checksum before writing them to the package cache or unpacking a cached copy.

Red Hat VEX · CVE-2026-96618

fixed0affected0not affected1

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

  • Identify exposed assets running affected vendor/product/version combinations.
  • Prioritize based on EPSS, PoC availability, and external exposure.
  • Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

VendorProductVersionsStatus
hexpmhex0.11.2 to < 2.5.2Vulnerable
hexpmhex51ea632424fb6ea8765148f96dc25dfeb526b1f8Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Scope

X

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

A

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactSource
2.1CVSS 4.0low——hexpm (CNA)
4.3CVSS 3.1medium——Red Hat (VEX)

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-409 · Improper Handling of Highly Compressed Data (Data Amplification)

  • DoS: Amplification
  • DoS: Crash, Exit, or Restart
  • DoS: Resource Consumption (CPU)
  • DoS: Resource Consumption (Memory)

CWE-770 · Allocation of Resources Without Limits or Throttling

  • DoS: Resource Consumption (CPU)
  • DoS: Resource Consumption (Memory)
  • DoS: Resource Consumption (Other)

Mitigation: Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.

Weakness & attack patterns

  • CWE-409
  • CWE-770

Inferred from the weakness class — not observed against this CVE.

CAPEC-125 · FloodingCAPEC-130 · Excessive Allocation
  • T1498.001Network Denial of Service: Direct Network Flood
  • T1499Endpoint Denial of Service
  • T1499.003Endpoint Denial of Service: Application Exhaustion Flood

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

1

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

  • Search application, proxy, and WAF logs for requests touching /5, /1, /2, /3, //github.com/hexpm/hex_core/security/advisories/GHSA-7c4r-cgf9-9jmq.
  • Prioritize edge telemetry for network-reachable hex.
  • Monitor for scanner or exploit-pattern traffic after 1 public PoC repositories were reported.
web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

  1. 2026

  2. Added · CVSS 3.1 2.1 (AV:N)

    Oct 12, 2026 · NVD

  3. Initial · CVE published

    Oct 12, 2026 · NVD

  4. CVE published by MITRE.

    Oct 12, 2026 · SOCRadar CTI

References

8 on the record

Elsewhere on this site

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 record1

What should defenders know first?

CVE-2026-96618 is Hex exhausts memory and disk on oversized or compressed responses from an untrusted mirror, a low vulnerability affecting hex from hexpm. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-96618. Public exploit evidence is: 1 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 2.1 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.