CVE-2026-18839: popt: integer underflow in help formatting causes local DoS

LOW

Published August 5, 2026

CISO Take

CVE-2026-18839 is an integer underflow (CWE-191) in the popt command-line parsing library that can crash an application, or stop it displaying help, when it prints help text for option tables wider than the terminal. It is low severity (CVSS 2.2) because it needs local access, low privileges, high attack complexity and a user action, and it affects only availability. There is no known public exploit, no Nuclei template, no CISA KEV listing and no EPSS score. The AI relevance is indirect: popt is bundled in many Red Hat OpenShift AI (rhoai) operator and controller container images, and the library has 695 downstream dependents. Treat this as routine patch hygiene: apply Red Hat advisory RHSA-2026:77932 through your normal container image refresh cycle and do not escalate it.

Sources:NVDRed HatOpenSSF

What is the risk?

Low risk. The CVSS vector is AV:L/AC:H/PR:L/UI:R with impact limited to low availability loss, and there is no confidentiality or integrity impact. No exploit, scanner template, KEV listing or SSVC decision exists. The crash is limited to the CLI process that prints help, so it does not take down a long-running service. The popt package has an OpenSSF Scorecard of 5.4/10 and 142 other CVEs, which points to a modest overall hygiene concern but not to urgency for this issue.

How does the attack unfold?

Local Access

A low-privileged user obtains a shell in a container or on a node that includes the vulnerable popt library.

Trigger

The user runs a popt-based tool with a help option table wider than the terminal, causing the integer underflow.

Impact

The application crashes or fails to display help, giving a limited denial of service for that invocation.

Local Access

A low-privileged user obtains a shell in a container or on a node that includes the vulnerable popt library.

Trigger

The user runs a popt-based tool with a help option table wider than the terminal, causing the integer underflow.

Impact

The application crashes or fails to display help, giving a limited denial of service for that invocation.

What systems are affected?

Package	Ecosystem	Vulnerable Range	Patched
MLflow	pip	—	No patch
28.6KOpenSSF 5.4695 dependentsPushed 5d ago15% patched~68d to patchFull package profile →
MLflow	pip	—	No patch
28.6KOpenSSF 5.4695 dependentsPushed 5d ago15% patched~68d to patchFull package profile →
MLflow	pip	—	No patch
28.6KOpenSSF 5.4695 dependentsPushed 5d ago15% patched~68d to patchFull package profile →
openshift/ose-rhel-coreos-8	—	—	No patch
openshift/ose-rhel-coreos-9	—	—	No patch
popt	—	—	No patch
popt-main	—	—	No patch
rhoai/odh-ai-gateway-operator-rhel9	—	—	No patch
rhoai/odh-core-bff-rhel9	—	—	No patch
rhoai/odh-dashboard-operator-rhel9	—	—	No patch
rhoai/odh-dashboard-rhel9	—	—	No patch
rhoai/odh-data-science-pipelines-operator-controller-rhel9	—	—	No patch
rhoai/odh-kf-notebook-controller-rhel9	—	—	No patch
rhoai/odh-kserve-controller-rhel9	—	—	No patch
rhoai/odh-kserve-llmisvc-controller-rhel9	—	—	No patch
rhoai/odh-kserve-module-operator-rhel9	—	—	No patch
rhoai/odh-kube-rbac-proxy-rhel9	—	—	No patch
rhoai/odh-kuberay-operator-controller-rhel9	—	—	No patch
rhoai/odh-llama-stack-k8s-operator-rhel9	—	—	No patch
rhoai/odh-maas-controller-rhel9	—	—	No patch
rhoai/odh-mod-arch-agent-ops-rhel9	—	—	No patch
rhoai/odh-mod-arch-automl-rhel9	—	—	No patch
rhoai/odh-mod-arch-autorag-rhel9	—	—	No patch
rhoai/odh-mod-arch-eval-hub-rhel9	—	—	No patch
rhoai/odh-mod-arch-gen-ai-rhel9	—	—	No patch
rhoai/odh-mod-arch-maas-rhel9	—	—	No patch
rhoai/odh-mod-arch-model-registry-rhel9	—	—	No patch
rhoai/odh-model-controller-rhel9	—	—	No patch
rhoai/odh-model-registry-operator-rhel9	—	—	No patch
rhoai/odh-model-serving-api-rhel9	—	—	No patch
rhoai/odh-notebook-controller-rhel9	—	—	No patch
rhoai/odh-ogx-k8s-operator-rhel9	—	—	No patch
rhoai/odh-ogx-module-operator-rhel9	—	—	No patch
rhoai/odh-training-operator-rhel9	—	—	No patch
rhoai/odh-trustyai-service-operator-rhel9	—	—	No patch
rhoai/odh-workbenches-operator-rhel9	—	—	No patch

How severe is it?

CVSS 3.1

2.2 / 10

EPSS

N/A

Exploitation Status

No known exploitation

Sophistication

Moderate

What is the attack surface?

AVLocal

ACHigh

PRLow

UIRequired

SUnchanged

CNone

INone

ALow

What should I do?

1 step

1) Apply Red Hat advisory RHSA-2026:77932 and update to the fixed popt package. Rebuild or refresh the affected rhoai and OpenShift images. 2) Use your SBOM or image scanner to find images that include popt and track the vendor patched versions. 3) Limit shell access (exec, debug) in AI platform namespaces and on nodes to trusted administrators. 4) No special detection is needed. Watch for unexpected crashes of CLI tools when run with --help. 5) Fold the update into the next regular maintenance window.

How is it classified?

DoSFramework

Which compliance frameworks are affected?

This CVE is relevant to:

ISO 42001

A.6.2.6-AI system operation and monitoring

NIST AI RMF

MANAGE 2.3-Mechanisms to respond to and recover from unknown risks

Frequently Asked Questions

What is CVE-2026-18839?

Is CVE-2026-18839 actively exploited?

No confirmed active exploitation of CVE-2026-18839 has been reported, but organizations should still patch proactively.

How to fix CVE-2026-18839?

1) Apply Red Hat advisory RHSA-2026:77932 and update to the fixed popt package. Rebuild or refresh the affected rhoai and OpenShift images. 2) Use your SBOM or image scanner to find images that include popt and track the vendor patched versions. 3) Limit shell access (exec, debug) in AI platform namespaces and on nodes to trusted administrators. 4) No special detection is needed. Watch for unexpected crashes of CLI tools when run with --help. 5) Fold the update into the next regular maintenance window.

What systems are affected by CVE-2026-18839?

This vulnerability affects the following AI/ML architecture patterns: model serving, training pipelines, MLOps platforms, Kubernetes AI operators, notebook environments.

What is the CVSS score for CVE-2026-18839?

CVE-2026-18839 has a CVSS v3.1 base score of 2.2 (LOW).

What is the AI security impact?

Affected AI Architectures

model servingtraining pipelinesMLOps platformsKubernetes AI operatorsnotebook environments

Compliance Controls Affected

ISO 42001: A.6.2.6

NIST AI RMF: MANAGE 2.3

What are the technical details?

Original Advisory

An integer underflow was found in the popt library when formatting help text for option tables that exceed the terminal width. A local user who can cause an application to print help under those conditions may cause that application to crash or fail to display help, resulting in a denial of service of the affected application.

Exploitation Scenario

A low-privileged local user with shell access to a container or node in an OpenShift AI cluster runs a popt-based tool with a long option table in a terminal sized to trigger the width calculation underflow. The tool crashes or fails to show help. The attacker gains no code execution or data access, and the effect is limited to denial of service for that one invocation. Large-scale disruption of AI workloads is not realistic with this flaw.

Weaknesses (CWE)

CWE-191Integer Underflow (Wrap or Wraparound)

CWE-191 — Integer Underflow (Wrap or Wraparound): The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

Source: MITRE CWE corpus.