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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.0 · CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-25598: 0.34% estimated exploitation activity in the next 30 days; percentile 28.17 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

9 Feb 2026, 17:19 UTC

Last modified by the source

9 Feb 2026, 22:39 UTC

Source last checked

26 Oct 2026, 17:08 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cpmj-h4f6-r6pq

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# Patch Next advisory brief: CVE-2026-25598

Advisory: Harden-Runner: Bypassing Logging of Outbound Connections Using sendto, sendmsg, and sendmmsg in Harden-Runner (Community Tier)
IDs: CVE-2026-25598, GHSA-cpmj-h4f6-r6pq
Record: https://patchnext.com/advisories/cve-2026-25598 (revision 1, source checked 26 Oct 2026, 17:08 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: step-security/harden-runner 2.14.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- GitHub Actions step-security/harden-runner: affected < 2.14.2; fixed in 2.14.2

## Suggested inspection (read-only)
- GitHub Actions step-security/harden-runner: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on step-security/harden-runner.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cpmj-h4f6-r6pq (GitHub-reviewed advisory GHSA-cpmj-h4f6-r6pq lists affected ranges: GitHub Actions step-security/harden-runner >=0 <2.14.2)

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