How severe is CVE-2026-39396?

CVE-2026-39396 has a CVSS score of 3.1/10, rated LOW. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-39396?

CVE-2026-39396 affects the following packages: github.com/openbao/openbao (Go). Ecosystems affected: Go.

How do I fix CVE-2026-39396?

Update github.com/openbao/openbao to 0.0.0-20260420180337-2b2a901aa9f7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39396 is resolved across your whole dependency graph.

How do I detect CVE-2026-39396 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/openbao/openbao. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-39396 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-39396?

O3 pinpoints whether CVE-2026-39396 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-39396 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-39396 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-39396 published, and has it been updated?

CVE-2026-39396 was published on April 21, 2026 and was last updated on July 31, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

CVE-2026-39396

LOW

CVE-2026-39396 is a low-severity (CVSS 3.1) vulnerability in github.com/openbao/openbao. O3 Security confirms whether CVE-2026-39396 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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

Also known asBIT-openbao-2026-39396GHSA-r65v-xgwc-g56jGO-2026-5609

Published

Apr 21, 2026

Updated

Jul 31, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Real-World Exposure

1 pkg affected

🐹github.com/openbao/openbao

Real-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

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/openbao/openbao`	all versions	0.0.0-20260420180337-2b2a901aa9f7

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/openbao/openbao. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/openbao/openbao to 0.0.0-20260420180337-2b2a901aa9f7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39396 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-39396 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-39396. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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 mi

O3 Security · Impact-Aware SCA

Is CVE-2026-39396 in your dependencies?

O3 detects CVE-2026-39396 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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