CVE-2026-31886: Dagu: Path Traversal via `dagRunId` in Inline DAG Execution

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.5%, percentile 42: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 42% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes github.com/dagu-org/dagu (Go) <= 2.2.4, no fixed version listed. Check your lockfile, including transitive dependencies.

What it is

Dagu is a workflow engine with a built-in Web user interface. Prior to 2.2.4, the dagRunId request field accepted by the inline DAG execution endpoints is passed directly into filepath.Join to construct a temporary directory path without any format validation. Go's filepath.Join resolves .. segments lexically, so a caller can supply a value such as ".." to redirect the computed directory outside the intended /tmp/ / path. A deferred cleanup function that calls os.RemoveAll on that directory then runs unconditionally when the HTTP handler returns, deleting whatever directory the traversal resolved to. With dagRunId set to "..", the resolved directory is the system temporary directory (/tmp on Linux). On non-root deployments, os.RemoveAll("/tmp") removes all files in /tmp owned by the dagu process user, disrupting every concurrent dagu run that has live temp files. On root or Docker deployments, the call removes the entire contents of /tmp, causing a system-wide denial of service. This vulnerability is fixed in 2.2.4.

From the GitHub advisory

1. Vulnerability Summary

The dagRunId request field accepted by the inline DAG execution endpoints is passed directly into filepath.Join to construct a temporary directory path without any format validation. Go's filepath.Join resolves .. segments lexically, so a caller can supply a value such as ".." to redirect the computed directory outside the intended /tmp/ / path. A deferred cleanup function that calls os.RemoveAll on that directory then runs unconditionally when the HTTP handler returns, deleting whatever directory the traversal resolved to.

With dagRunId set to "..", the resolved directory is the system temporary directory (/tmp on Linux). On non-root deployments, os.RemoveAll("/tmp") removes all files in /tmp owned by the dagu process user, disrupting every concurrent dagu run that has live temp files. On root or Docker deployments, the call removes the entire contents of /tmp, causing a system-wide denial of service.

2. This Is Not a Duplicate of Existing Advisories

Two security advisories are already published for dagu. This vulnerability is distinct from both.

Weakness type: CWE-22.

Product: github.com/dagu-org/dagu (Go) · Assigned by: GitHub_M · Published: 2026-03-13

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.50% probability of exploitation activity in the next 30 days; percentile 42.

Timeline

• 2026-03-13 — CVE record last updated
• 2026-03-13 — CVE record published by GitHub_M
• 2026-03-13 — GitHub-reviewed advisory GHSA-m4q3-457p-hh2x published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-m4q3-457p-hh2x github.com
2. CVE.org record CVE-2026-31886 cve.org
3. NVD entry CVE-2026-31886 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. pkg.go.dev pkg.go.dev

Critical Go advisories · Today’s Security Digest