OpenBao: Decompression Bomb via Unbounded Copy in OCI Plugin Extraction (DoS)

Exploitation

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

CVSS

3.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-39396: 0.22% estimated exploitation activity in the next 30 days; percentile 12.40 (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 ExtractPluginFromImage() in OpenBao's OCI plugin downloader extracts a plugin binary from a container image by streaming decompressed tar data via io.Copy with no upper bound on the number of bytes written. An attacker who controls or compromises the OCI registry referenced in the victim's configuration can serve a crafted image containing a decompression bomb that decompresses to an arbitrarily large file. The SHA256 integrity check occurs after the full file is written to disk, meaning the hash mismatch is detected only after the damage (disk exhaustion) has already occurred. This allow the attacker to replace legit plugin image with no need to change its signature. Details Root cause helper/pluginutil/oci/downloader.go:301: io.Copy() reads until EOF with no size limit. The tar header.Size field is never validated before the copy, and mutate.Extract decompresses all gzip layers in memory/streaming, resulting in unbounded decompression-to-disk. PoC 1. Set up a malicious OCI…

Published by the source

21 Apr 2026, 18:24 UTC

Last modified by the source

21 Apr 2026, 18:24 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-r65v-xgwc-g56j

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-39396

Advisory: OpenBao: Decompression Bomb via Unbounded Copy in OCI Plugin Extraction (DoS)
IDs: CVE-2026-39396, GHSA-r65v-xgwc-g56j
Record: https://patchnext.com/advisories/cve-2026-39396 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/openbao/openbao 0.0.0-20260420180337-2b2a901aa9f7. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/openbao/openbao: affected < 0.0.0-20260420180337-2b2a901aa9f7; fixed in 0.0.0-20260420180337-2b2a901aa9f7

## Suggested inspection (read-only)
- Go github.com/openbao/openbao: 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 github.com/openbao/openbao.
- 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-r65v-xgwc-g56j (GitHub-reviewed advisory GHSA-r65v-xgwc-g56j lists affected ranges: Go github.com/openbao/openbao >=0 <0.0.0-20260420180337-2b2a901aa9f7)

Commands are suggestions: review each one before running it.