TI-2026-66002 Aliases CVE-2026-97876 GHSA-v555-hf4g-q6pc

Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address

LOW 29CWE-822Published 2026-10-02 · Updated 2026-10-02

Key facts

Attack vector: Local
Privileges required: High
User interaction: None
Attack complexity: High
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Partial Red Hat: 6 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-822 and the CVSS impact.

Summary

A local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command. GRUB does not validate that the base address corresponds to a UART device, rather than being an arbitrary memory address. This allows an attacker to trick GRUB into writing non-arbitrary data at an attacker-controlled address, including resetting the grub_file_verifiers list in a way that disables the subsequent verification of loaded modules.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00115 1st percentileScored 2026-11-07

Fix Partial grub2 (GNU): 2.16Red Hat: 6 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
GNU	grub2	2.12 to before 2.16	2.16	Patch available	CNA

grub2 VendorGNU Affected 2.12 to before 2.16 Fixed in 2.16 Patch available CNA

Remediation

Fix · CNA grub2 (GNU) Fixed in 2.16

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat Enterprise Linux 10	Affected	No fix yet: Fix deferred
Red Hat Enterprise Linux 7	Affected	No fix yet: Fix deferred
Red Hat Enterprise Linux 8	Affected	No fix yet: Fix deferred
Red Hat Enterprise Linux 9	Affected	No fix yet: Fix deferred
Red Hat OpenShift Container Platform 4	Affected	No fix yet: Fix deferred
Red Hat OpenShift Container Platform 5	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-97876
2026-10-03 Alias added: GHSA-v555-hf4g-q6pc
2026-11-06 Affected versions changed · Red Hat

References

Patch 1

https://gitlab.freedesktop.org/gnu-grub/grub/-/commit/26beaa3b2720fefdc4d04c1ae209b776fe6848d6

Other 1

https://www.openwall.com/lists/oss-security/2026/09/13/5

TI-2026-19388 telnetd in GNU Inetutils through 2.7 allows remote authentication bypass via a "-f root"… KEVCVSS 3.1CRITICAL 9.8
TI-2014-05975 GNU Bash through 4.3 bash43-025 processes trailing strings after certain malformed… KEVCVSS 3.1CRITICAL 9.8
TI-2014-05157 GNU Bash through 4.3 processes trailing strings after function definitions in the values… KEVCVSS 3.1CRITICAL 9.8
TI-2014-05164 GNU Bash through 4.3 bash43-026 does not properly parse function definitions in the… KEVCVSS 3.1HIGH 8.8
TI-2023-04522 Glibc: buffer overflow in ld.so leading to privilege escalation KEVCVSS 3.1HIGH 7.8
TI-2009-03392 The TLS protocol, and the SSL protocol 3.0 and possibly earlier, as used in Microsoft… CVSS 3.1CRITICAL 9.8

See all 1272 →

Sources

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