OpenBMC IPMI Authentication Bypass via Default userKey and Stale Challenge Value

published 2026-09-15 54 d ago modified 2026-09-18 51 d ago also EUVD-2026-78573

cvss: 8.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits: 0; none known

OpenBMC's IPMI implementation, phosphor-net-ipmid, contains a logic flaw in which an unauthenticated client can force the RAKP Message 1 handler to return before it overwrites the authentication object's constructor defaults. The IPMI service then accepts a RAKP Message 3 whose HMAC is computed with the constant 20-byte 'userKey' initialized from the string '0penBmc' and an often-predictable 'bmcRandomNum'. Several downstream vendors implement phosphor-net-ipmid as their IPMI stack, such as NVIDIA and H3C.

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 54 d ago (2026-09-15)

Exploit prediction

0.54% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	8.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

OpenBMC phosphor-net-ipmid

Classification

Weakness

CWE-798 Use of Hard-coded Credentials
CWE-457 Use of Uninitialized Variable

References

runzero.com /advisories/openbmc-ipmi-auth-bypass-rakp-cve-2026-16141/
third-party-advisory
runzero.com /blog/lights-out-exposed/
related

Sources

CVE List CVE-2026-16141
NVD CVE-2026-16141

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary