Low Cryptography

CVE-2026-39388 — OpenBao's Certificate Authentication Allows Token Renewal With Different Certificate

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.

Published Apr 20, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.1% (30-day exploitation probability)+0

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.14%

ahead of 3% of scored CVEs · Oct 14, 2026

Affects

Openbao

CVSS base

3.1

Low · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Openbao Openbao).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Exploitation requires user interaction: tighten email/web filtering and warn affected users.
Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Openbao	Openbao	< 2.5.3	Vulnerable	NIST National Vulnerability Database
Openbao	Openbao	version < 2.5.3	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

High

Privileges required

High

User interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
2.0	CVSS 4.0	Low	—	—	security-advisories@github.com via NIST National Vulnerability Database
2.0	CVSS 4.0	Low	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP
3.1	CVSS 3.1	Low	0.5	2.5	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-295 · Improper Certificate Validation

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.14%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Check TLS negotiations and unexpected certificates in the component’s traffic.

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · openbao/openbao
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 3.1
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Apr 20, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

github.com/openbao/openbao/security/advisories/GHSA-7ccv-rp6m-rffr
Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

Openbao
every CVE for this vendor

Cryptography
same class

CWE-295
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-42186 OpenBao's Namespace Deletion May Not Delete Data Properly May 14, 2026
Medium CVE-2026-39396 OpenBao has Decompression Bomb via Unbounded Copy in OCI Plugin Extraction (DoS) Apr 20, 2026
Medium CVE-2026-39946 OpenBao allows SQL Injection in PostgreSQL database secrets engine Apr 20, 2026
Low CVE-2026-40264 OpenBao's Token Store Allows Cross-Namespace Renewal, Revocation Apr 20, 2026
High CVE-2026-33757 OpenBao lacks user confirmation for OIDC direct callback mode Mar 27, 2026
Medium CVE-2026-33758 OpenBao has Reflected XSS in its OIDC authentication error message Mar 27, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-39388 is "OpenBao's Certificate Authentication Allows Token Renewal With Different Certificate", rated Low. It affects Openbao (Openbao); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 3.1 describes technical severity. EPSS 0.14% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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