CVE-2026-39388

Description

OpenBao is an open source identity-based secrets management system. Prior to version 2.5.3, OpenBao's Certificate authentication method, when a token renewal is requested and `disable_binding=true` is set, attempts to verify the current request's presented mTLS certificate matches the original. Token renewals for other authentication methods do not require any supplied login information. Due to incorrect matching, the certificate authentication method would allow renewal of tokens for which the attacker had a sibling certificate+key signed by the same CA, but which did not necessarily match the original role or the originally supplied certificate. This implies an attacker could still authenticate to OpenBao in a similar scope, however, token renewal implies that an attacker may be able to extend the lifetime of dynamic leases held by the original token. This attack requires knowledge of either the original token or its accessor. This vulnerability is original from HashiCorp Vault. This is addressed in v2.5.3. As a workaround, ensure privileged roles are tightly scoped to single certificates.

CVSS v3.1 Score

3.1

LOW

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

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-295 CWE-295

Affected Products

Vendor	Product	Versions
openbao	openbao	< 2.5.3

References

Advisories & Patches

https://github.com/openbao/openbao/security/advisories/GHSA-7ccv-rp6m-rffr

Frequently Asked Questions

What is CVE-2026-39388? +

OpenBao is an open source identity-based secrets management system. Prior to version 2.5.3, OpenBao's Certificate authentication method, when a token renewal is requested and `disable_binding=true` is set, attempts to verify the current request's presented mTLS certificate matches the original. Token renewals for other authentication methods do not require any supplied login information. Due to incorrect matching, the certificate authentication method would allow renewal of tokens for which the attacker had a sibling certificate+key signed by the same CA, but which did not necessarily match the original role or the originally supplied certificate. This implies an attacker could still authenticate to OpenBao in a similar scope, however, token renewal implies that an attacker may be able to extend the lifetime of dynamic leases held by the original token. This attack requires knowledge of either the original token or its accessor. This vulnerability is original from HashiCorp Vault. This is addressed in v2.5.3. As a workaround, ensure privileged roles are tightly scoped to single certificates. It has a CVSS v3.1 base score of 3.1 (LOW).

How severe is CVE-2026-39388? +

CVE-2026-39388 has a CVSS v3.1 score of 3.1 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-39388? +

CVE-2026-39388 affects products from openbao, specifically: openbao. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-39388? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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