CVE-2026-35580: Emissary is a P2P based data-driven workflow engine

This month

CRITICAL 9.1UPGRADE

CVE-2026-35580 is a critical-severity flaw (CVSS 9.1) affecting emissary. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Emissary is a P2P based data-driven workflow engine. Prior to 8.39.0, GitHub Actions workflow files contained shell injection points where user-controlled workflow_dispatch inputs were interpolated directly into shell commands via ${{ }} expression syntax. An attacker with repository write access could inject arbitrary shell commands, leading to repository poisoning and supply chain compromise affecting all downstream users. This vulnerability is

Why this priority

Critical severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-77
Published	2026-04-07
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: nsa

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-07 17:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

nsa emissary UPGRADE

Affected: >= 5.10.0 and <= 8.38.0

Fixed in: newer than 8.38.0

Safe to downgrade to: a release before 5.10.0

1. Check installed version

apt-cache policy emissary || rpm -q emissary || emissary --version

2. UPGRADE to newer than 8.38.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade emissary

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade emissary

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.10.0 (Debian / Ubuntu)

apt-cache madison emissary sudo apt install emissary=<VERSION_BEFORE_5.10.0> sudo apt-mark hold emissary

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list emissary sudo dnf downgrade emissary-<VERSION_BEFORE_5.10.0> sudo dnf versionlock add emissary

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-35580?

emissary: upgrade to newer than 8.38.0. Exact commands for each OS are on this page.

Is CVE-2026-35580 being exploited?

CVE-2026-35580 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-35580 affect?

CVE-2026-35580 affects emissary. Severity is critical (CVSS 9.1). Emissary is a P2P based data-driven workflow engine. Prior to 8.39.0, GitHub Actions workflow files contained shell injection points where user-controlled workflow_dispatch inputs were interpolated directly into shell commands via ${{ }} ex

How urgent is CVE-2026-35580?

Priority 49/100. Critical severity; Public exploit reference

Software pages

GitHub vulnerabilities

Related CVEs

CVE-2026-35582 HIGH 8.8 UPGRADE Emissary is a P2P based data-driven workflow engine
CVE-2026-35581 HIGH 7.2 UPGRADE Emissary is a P2P based data-driven workflow engine
CVE-2026-35583 MEDIUM 5.3 UPGRADE Emissary is a P2P based data-driven workflow engine
CVE-2026-35571 MEDIUM 4.8 UPGRADE Emissary is a P2P based data-driven workflow engine

References

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