CVE-2026-44885 is a medium-severity (CVSS 5.5) Path Traversal vulnerability in github.com/portainer/portainer. A fix is available for github.com/portainer/portainer — see the affected versions and patch details below.
Portainer: Path traversal in backup archive extraction allows arbitrary file write
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-2026-44885.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-44885 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/portainer/portainerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Portainer's backup restore feature accepts a .tar.gz archive and extracts it to a target directory on the server. The extraction function (ExtractTarGz in api/archive/targz.go) constructed output paths using filepath.Clean(filepath.Join(outputDirPath, header.Name)). This combination does not prevent directory traversal — a tar entry named ../../etc/cron.d/evil resolves to a path outside the extraction root, so a crafted archive can write files to arbitrary locations on the server filesystem.
Severity
Medium
CWE-22 — Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Exploitation requires administrator access to Portainer's backup restore endpoint. An administrator who is deceived into restoring a malicious archive, or whose credentials are compromised, can use this path to write files outside the Portainer data directory.
Affected Versions
The vulnerability exists in every Portainer release prior to 2.39.0 — ExtractTarGz has used filepath.Clean(filepath.Join()) since it was introduced. The fix shipped with 2.39.0 (patched on develop before the 2.39 branch cut); 2.34.x–2.38.x STS releases are also affected but are end-of-life and will not receive a fix.
| Branch | First vulnerable | Fixed in |
|---|---|---|
| 2.33.x (LTS) | 2.33.0 | 2.33.8 |
Portainer 2.39.0 and later are not affected — the fix was present from the initial 2.39.0 release. All releases prior to 2.33.0 are end-of-life and will not receive a fix; users on EOL versions should upgrade to a supported release.
Workarounds
Administrators who cannot immediately upgrade should:
- Only restore archives from trusted sources. Do not restore archives received from untrusted parties or transmitted over unencrypted channels.
- Use backup encryption. Portainer's optional backup encryption requires the correct passphrase to decrypt before extraction; an attacker without the passphrase cannot craft a valid encrypted archive.
Neither of these replaces the fix.
Affected Code
ExtractTarGz in api/archive/targz.go constructed output paths without safe containment:
// api/archive/targz.go (pre-fix)
case tar.TypeReg:
p := filepath.Clean(filepath.Join(outputDirPath, header.Name))
filepath.Join resolves ../ components lexically and filepath.Clean normalises the result, but neither verifies the final path remains inside outputDirPath. The fix replaces this with filesystem.JoinPaths, which forces all path components to be relative to the trusted root:
// api/archive/targz.go (post-fix)
case tar.TypeReg:
p := filesystem.JoinPaths(outputDirPath, header.Name)
Impact
- Arbitrary file write at any path accessible to the Portainer process (typically root in containerised deployments), overriding filesystem boundaries of the data directory.
- Potential host persistence by writing to cron directories, SSH authorised key files, or executable paths, depending on how the container is configured and what host paths are accessible.
The practical severity is reduced because exploitation requires administrative privileges within Portainer.
Timeline
- 2026-02-16: Fix merged to develop (#1875).
- 2026-02-25: 2.39.0 released with fix.
- 2026-05-07: 2.33.8 released with backport fix.
Credits
Reported by Kolega.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/portainer/portainer | ≥ 2.33.0&&< 2.33.8 | 2.33.8go get github.com/portainer/portainer@v2.33.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/portainer/portainer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/portainer/portainer to 2.33.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44885 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44885 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-44885. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-44885 in your dependencies?
O3 Security finds CVE-2026-44885 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.