How severe is CVE-2026-25598?

No CVSS score has been assigned to CVE-2026-25598 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-25598?

CVE-2026-25598 affects the following packages: step-security/harden-runner (GitHub Actions). Ecosystems affected: GitHub Actions.

How do I fix CVE-2026-25598?

Update step-security/harden-runner to 2.14.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25598 is resolved across your whole dependency graph.

How do I detect CVE-2026-25598 in my GitHub Actions dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for step-security/harden-runner, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-25598 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-25598 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-25598 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-25598?

CVE-2026-25598 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 28th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-25598?

CVE-2026-25598 is classified as CWE-778 (CWE-778). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-25598 published, and has it been updated?

CVE-2026-25598 was published on February 9, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 GitHub Actions

Not in CISA KEV

CVE-2026-25598 — harden-runner

Fix: step-security/harden-runner@5ef0c07

CVE-2026-25598 is a CWE-778 vulnerability in step-security/harden-runner. A fix is available for step-security/harden-runner — see the affected versions and patch details below.

Bypassing Logging of Outbound Connections Using sendto, sendmsg, and sendmmsg in Harden-Runner (Community Tier)

Also known asGHSA-cpmj-h4f6-r6pq

Published

Feb 9, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-25598.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk-0.01%

Lower risk than most CVEs28th percentile — riskier than 28% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

📦step-security/harden-runner

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects GitHub Actions packages — download data is not available via public APIs for these ecosystems.

Description

Summary

A security vulnerability has been identified in the Harden-Runner GitHub Action (Community Tier) that allows outbound network connections to evade audit logging. Specifically, outbound traffic using the sendto, sendmsg, and sendmmsg socket system calls can bypass detection and logging when using egress-policy: audit.

Note: This vulnerability only affects audit mode. When using egress-policy: block, these connections are properly blocked. It requires the attacker to already have code execution capabilities within the GitHub Actions workflow (e.g., through workflow injection or compromised dependencies)

Affected Versions

Harden-Runner Community Tier: All versions prior to v2.14.2
Harden-Runner Enterprise Tier: NOT AFFECTED

Severity

Medium - This vulnerability affects audit logging capabilities but requires the attacker to already have code execution within the workflow.

Impact

When Harden-Runner is configured in audit mode (egress-policy: audit), attackers with the ability to execute arbitrary code in a workflow can:

Send outbound network traffic without generating audit logs
Bypass network monitoring for UDP-based communications

Important: This vulnerability requires the attacker to already have code execution capabilities within the GitHub Actions workflow (e.g., through workflow injection or compromised dependencies).

Technical Details

The vulnerability stems from incomplete monitoring coverage of certain socket-related system calls. Specifically, the following system calls can be used to send UDP traffic without triggering audit events:

sendto()
sendmsg()
sendmmsg()

An attacker with code execution in a workflow can compile and execute native code that uses these system calls to establish covert communication channels.

Affected Users

This vulnerability ONLY affects users of the Harden-Runner Community Tier.

The Harden-Runner Enterprise Tier is NOT vulnerable to this bypass technique.

Remediation

For Community Tier Users

Upgrade to Harden-Runner v2.14.2 or later. This version includes fixes for the logging bypass vulnerability.

For Enterprise Tier Users

No action required. Enterprise tier customers are not affected by this vulnerability.

Credit

We would like to thank Devansh Batham for responsibly disclosing this vulnerability through our security reporting process. Devansh was communicative throughout the process and verified the fix before the fix before it was made public.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦GitHub Actions	`step-security/harden-runner`	all versions	2.14.2

Affected Products

1 product · 1 configurations

Application

harden-runnerstepsecurity

< 2.14.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for step-security/harden-runner, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update step-security/harden-runner to 2.14.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25598 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This vulnerability is rated as Moderate, in part due to the following necessary preconditions for exploitation to be possible: 1. Harden-runner must be in audit mode. 2. The attacker must already have code execution capabilities within the GitHub Actions workflow. Note: When using egress-policy: block, these…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Source: Red Hat security advisory for CVE-2026-25598 (CC BY 4.0)

Frequently Asked Questions

## Summary A security vulnerability has been identified in the Harden-Runner GitHub Action (Community Tier) that allows outbound network connections to evade audit logging. Specifically, outbound traffic using the `sendto`, `sendmsg`, and `sendmmsg` socket system calls can bypass detection and logging when using `egress-policy: audit`. **Note:** This vulnerability only affects audit mode. When using `egress-policy: block`, these connections are properly blocked. It requires the attacker to already have code execution capabilities within the GitHub Actions workflow (e.g., through workflow i