CVE-2026-39396 OpenBao has Decompression Bomb via Unbounded Copy in OCI Plugin Extraction (DoS)
An attacker can cause disk exhaustion and denial of service by serving a crafted OCI image with a decompression bomb to OpenBao's plugin extractor.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-39396?
CVE-2026-39396 is a low-severity denial of service vulnerability in openbao, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
OpenBao is an open source identity-based secrets management system. Prior to version 2.5.3, `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. Version 2.5.3 contains a patch.
Which versions are affected by CVE-2026-39396?
4 open source packages ship an affected version, including github.com/openbao/openbao and openbao. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/openbao/openbao Go | All versions | 0.0.0-20260420180337-2b2a901aa9f7 |
github.com/openbao/openbao Go | All versions | 0.0.0-20260420180337-2b2a901aa9f7 |
github.com/openbao/openbao Go | All versions | 0.0.0-20260420180337-2b2a901aa9f7 |
openbao Bitnami | All versions | 2.5.3 |
Products include Openbao Openbao.
How do I fix CVE-2026-39396?
Upgrade github.com/openbao/openbao to 0.0.0-20260420180337-2b2a901aa9f7 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-39396 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39396 exists.
Other vulnerabilities in openbao
- CVE-2026-33757 OpenBao lacks user confirmation for OIDC direct callback mode
- CVE-2026-33758 OpenBao has Reflected XSS in its OIDC authentication error message
- CVE-2025-54997 OpenBao: Privileged Operator May Execute Code on the Underlying Host
- CVE-2025-64761 OpenBao Privileged Operator Identity Group Root Escalation
- CVE-2025-59043 OpenBao vulnerable to denial of service via malicious JSON request processing
Sources
Also known as BIT-openbao-2026-39396, GHSA-r65v-xgwc-g56j, GO-2026-5609.