CVE-2026-39396

CVE-2026-39396 is a low-severity vulnerability in Openbao with a CVSS 3.x base score of 3.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

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.

Frequently asked questions

What is CVE-2026-39396?
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.
How severe is CVE-2026-39396?
CVE-2026-39396 has a CVSS 3.x base score of 3.1, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-39396 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39396?
CVE-2026-39396 affects Openbao. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39396?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-39396 have an EU (EUVD) identifier?
Yes. CVE-2026-39396 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-24031.
When was CVE-2026-39396 published?
CVE-2026-39396 was published on 2026-04-21 and last updated on 2026-06-17.

References

Affected products (1)

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