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Fencer Intel
low 2.3

CVE-2026-81856 json

Terminal escape sequence injection in Hex via unneutralized server-supplied output

published 30d ago modified 14h ago also EUVD-2026-97512 , GHSA-fpmj-3cxg-p766

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository hexpm/hex. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
2.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 34%
public exploits
0
none known

Summary

Improper Neutralization of Escape, Meta, or Control Sequences vulnerability in hexpm hex allows a malicious package publisher or a hostile repository server to inject terminal control sequences into the output of Mix tasks.

Hex prints strings supplied by the package repository and the documentation search service straight to the terminal through Hex.Shell.info/1 and Hex.Shell.error/1, neutralizing no control characters. Affected sinks span package metadata and configuration snippets in mix hex.info, search results in mix hex.package search and mix hex.search, owner and organization listings, publish and sponsor URLs, the authenticated username in mix hex.user, policy identities in mix hex.policy, and API error bodies rendered by Hex.Utils.print_error_result/1. A malicious package can embed ANSI escape sequences (cursor movement, line erase, carriage returns, OSC 52 clipboard writes) or Unicode bidirectional overrides in any of those fields, so the bytes reach the terminal unchanged, forging displayed URLs, package descriptions and suggested commands, concealing real output, or writing to the clipboard. No authentication or privileged position is required; only publishing a package.

This issue affects hex: from 0.0.1 before 2.5.2.

Patch / fix

  • hexpm hex 2.5.2
  • erlang-hex Debian 14 2.5.3-2

debian advisories DEBIAN-CVE-2026-81856

Is CVE-2026-81856 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-81856 updated cvss 4.3

hex: hex: Terminal output spoofing via unescaped control sequences

  • Red Hat Ansible Automation Orchestrator 2026 ansible-automation-platform/automation-orchestrator-backend-rhel9 Red Hat Confidential Cluster Operator confidential-clusters-beta/compute-pcrs-rhel9, confidential-clusters-beta/registration-server-rhel9, confidential-clusters-beta/attestation-key-register-rhel9, confidential-clusters-beta/confidential-cluster-rhel9-operator, confidential-clusters-beta/confidential-cluster-operator-bundle Red Hat Confidential Compute Attestation build-of-trustee/trustee-rhel9, agent-sandbox/agent-sandbox-router, openshift-sandboxed-containers/osc-podvm-builder-rhel9, openshift-sandboxed-containers/osc-podvm-payload-rhel9 Red Hat Lightspeed Services for Advanced Cluster Management lightspeed-services-acm/ocp-rules-rhel9 Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/vector-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9, openshift-lightspeed/lightspeed-to-dataverse-exporter-rhel9
    +24 more products
    Red Hat Pen Drive Powered by Red Hat Lightspeed pen-drive/pen-drive-scanner-rhel9 Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-27/hub-rhel9, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-27/gateway-rhel9, ansible-automation-platform-26/mcp-tools-rhel9, ansible-automation-platform-27/mcp-tools-rhel9, +20 more Red Hat Ansible Automation Platform Ansible Core 2 ansible-automation-platform/ee-minimal-rhel8, ansible-automation-platform/ee-minimal-rhel9, ansible-automation-platform-tech-preview/ee-minimal-rhel8, ansible-automation-platform-tech-preview/ee-minimal-rhel9 Red Hat Developer Hub 1 rhdh/rhdh-must-gather-rhel9 Red Hat Discovery 2 discovery/discovery-server-rhel9 Red Hat Enterprise Linux 7 firefox Red Hat Enterprise Linux 8 rls, rust, cargo, clippy, firefox, rustfmt, +15 more Red Hat Enterprise Linux 9 ctdb, rust, bootc, cargo, goose, samba, +73 more Red Hat Enterprise Linux 10 igvm, rust, bootc, goose, loupe, samba, +21 more Red Hat Enterprise Linux AI (RHEL AI) 3 rust Red Hat Enterprise Linux command line assistant rhel-cla/rhel-knowledge-bridge-rhel10 Red Hat Hardened Images rust, chunkah, netavark, openshell Red Hat Lightspeed Services for OCP lightspeed-services-ocp/ocp-rules-rhel9 Red Hat Offline Knowledge Portal offline-knowledge-portal/rhokp-rhel9 Red Hat OpenShift AI (RHOAI) rhoai/odh-feature-server-rhel9, rhai/base-image-torch-2.14-cpu-rhel9, rhai/base-image-torch-2.14-cuda-13.0-rhel9, rhoai/odh-ml-pipelines-runtime-generic-rhel9, rhoai/odh-model-registry-job-async-upload-rhel9 Red Hat OpenShift Container Platform 4 bootupd, afterburn, conmon-rs, rpm-ostree, rust-bootupd, rust-afterburn, +6 more Red Hat OpenShift Container Platform 5 conmon-rs, kata-containers Red Hat OpenShift Update Service openshift-update-service/openshift-update-service-rhel8 Red Hat OpenStack Platform 16.2 rabbitmq-server Red Hat OpenStack Platform 17.1 rabbitmq-server Red Hat Quay 3 quay/quay-rhel8, quay/quay-rhel9 Red Hat Satellite 6 satellite/iop-vmaas-rhel9, satellite/iop-advisor-engine-rhel9, satellite/iop-advisor-backend-rhel9 Red Hat Trusted Artifact Signer rhtas/tuffer-rhel9, rhtas/tuftool-rhel9 Red Hat Trusted Profile Analyzer rhtpa/rhtpa-rhel10, rhtpa/rhtpa-trustification-service-rhel9
    affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
26d ago

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 2.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
CNA 4.0 2.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/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

Affected products

  • hexpm hex

Classification

Weakness
  • CWE-150 Improper Neutralization of Escape, Meta, or Control Sequences

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of hexpm/hex published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.