CVE-2026-97876
Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address
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.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- High
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
6.4
Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address
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.
- Record
CVE-2026-97876- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-822
- Updated
- 2026-11-02
EUVDEUVD-2026-91376
6.4
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.
- Record
EUVD-2026-91376- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-v555-hf4g-q6pc
6.4
A local attacker with control over GRUB's configuration can bypass lockdown restrictions when...
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.
- Record
GHSA-v555-hf4g-q6pc- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-822
- Updated
- 2026-11-02
NVD
6.4
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.
- Record
CVE-2026-97876- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-822
- Updated
- 2026-11-02
OSVBELL-CVE-2026-97876
6.4
- Record
BELL-CVE-2026-97876- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSV
6.4
Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address
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.
- Record
CVE-2026-97876- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-822
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-97876
6.4
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.
- Record
DEBIAN-CVE-2026-97876- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-97876
6.4
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.
- Record
UBUNTU-CVE-2026-97876- CVSS 3.1
- 6.4 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
grubAlpaquita:23 |
2.12-r0 up to 2.12-r9 | 2.12-r9 |
grubAlpaquita:25 |
2.12-r10 up to 2.12-r12 | 2.12-r12 |
grubAlpaquita:stream |
2.12-r0 up to 2.14-r2 | 2.14-r2 |
grub2Debian:13 |
All versions, plus listed versions 2.12-92.12-9+deb13u12.12-9+deb13u22.12-9+hurd.12.14-1 Show 6 moreShow less2.14-22.14-32.14-42.14~git20250718.0e36779-12.14~git20250718.0e36779-22.16-1 |
None known |
grub2Debian:14 |
before 2.14-4, plus listed versions 2.12-92.12-9+hurd.12.14-12.14-22.14-32.14~git20250718.0e36779-12.14~git20250718.0e36779-2 |
2.14-4 |
grub2Ubuntu:Pro:14.04:LTS |
All versions, plus listed versions 2.00-19ubuntu22.00-19ubuntu32.00-19ubuntu42.00-202.00-21 Show 23 moreShow less2.00-222.02~beta2-52.02~beta2-62.02~beta2-72.02~beta2-82.02~beta2-92.02~beta2-9ubuntu12.02~beta2-9ubuntu1.12.02~beta2-9ubuntu1.22.02~beta2-9ubuntu1.32.02~beta2-9ubuntu1.42.02~beta2-9ubuntu1.52.02~beta2-9ubuntu1.62.02~beta2-9ubuntu1.72.02~beta2-9ubuntu1.82.02~beta2-9ubuntu1.112.02~beta2-9ubuntu1.122.02~beta2-9ubuntu1.142.02~beta2-9ubuntu1.152.02~beta2-9ubuntu1.162.02~beta2-9ubuntu1.172.02~beta2-9ubuntu1.202.02~beta2-9ubuntu1.21 |
None known |
grub2-signedUbuntu:Pro:14.04:LTS |
All versions, plus listed versions 1.221.231.241.251.26 Show 23 moreShow less1.271.301.311.321.331.341.34.11.34.21.34.31.34.41.34.51.34.61.34.71.34.81.34.91.34.131.34.141.34.161.34.171.34.181.34.201.34.221.34.24 |
None known |
grub2-signedUbuntu:16.04:LTS |
All versions, plus listed versions 1.551.561.571.581.59 Show 32 moreShow less1.611.621.631.641.651.661.66.11.66.21.66.61.66.71.66.81.66.91.66.111.66.121.66.141.66.151.66.161.66.171.66.181.66.191.66.201.66.211.66.221.66.231.66.261.66.271.66.281.66.291.167~16.04.11.167~16.04.21.167~16.04.41.167~16.04.6 |
None known |
grub2-unsignedUbuntu:16.04:LTS |
All versions, plus listed versions 2.04-1ubuntu442.04-1ubuntu44.12.04-1ubuntu44.1.2 |
None known |
grub2-signedUbuntu:18.04:LTS |
All versions, plus listed versions 1.851.861.871.891.91 Show 27 moreShow less1.921.931.93.11.93.21.93.31.93.41.93.51.93.71.93.81.93.101.93.111.93.131.93.141.93.151.93.161.93.181.93.191.93.201.93.211.93.221.93.241.167~18.04.11.167~18.04.31.167~18.04.51.173.2~18.04.11.187.2~18.04.11.187.3~18.04.1 |
None known |
Show 11 moreShow less
| Package | Affected | Fixed |
|---|---|---|
grub2-unsignedUbuntu:18.04:LTS |
All versions, plus listed versions 2.04-1ubuntu442.04-1ubuntu44.12.04-1ubuntu44.1.22.04-1ubuntu47.42.06-2ubuntu142.06-2ubuntu14.1 |
None known |
grub2-signedUbuntu:20.04:LTS |
All versions, plus listed versions 1.1281.1291.1301.1311.133 Show 27 moreShow less1.1341.1351.1361.1371.1381.1391.1401.1411.1421.142.11.142.31.142.41.142.51.142.61.142.81.142.91.142.101.142.111.1671.167.21.173.2~20.04.11.173.41.187.2~20.04.21.187.3~20.04.11.187.4~20.04.11.187.6~20.04.11.187.12~20.04 |
None known |
grub2-unsignedUbuntu:20.04:LTS |
All versions, plus listed versions 2.04-1ubuntu442.04-1ubuntu44.22.04-1ubuntu47.42.04-1ubuntu47.52.06-2ubuntu14 Show 4 moreShow less2.06-2ubuntu14.12.06-2ubuntu14.22.06-2ubuntu14.42.06-2ubuntu14.8 |
None known |
grub2-signedUbuntu:22.04:LTS |
All versions, plus listed versions 1.1731.1741.1761.1771.178 Show 8 moreShow less1.1791.1801.182~22.04.11.187.21.187.3~22.04.11.187.4~22.04.11.187.61.187.12 |
None known |
grub2-unsignedUbuntu:22.04:LTS |
All versions, plus listed versions 2.04-1ubuntu472.04-1ubuntu482.06-2ubuntu32.06-2ubuntu42.06-2ubuntu5 Show 8 moreShow less2.06-2ubuntu62.06-2ubuntu72.06-2ubuntu102.06-2ubuntu142.06-2ubuntu14.12.06-2ubuntu14.22.06-2ubuntu14.42.06-2ubuntu14.8 |
None known |
grub2-signedUbuntu:24.04:LTS |
All versions, plus listed versions 1.1971.1991.2011.2021.202.21.202.5 |
None known |
grub2-unsignedUbuntu:24.04:LTS |
All versions, plus listed versions 2.12~rc1-10ubuntu42.12~rc1-12ubuntu22.12-1ubuntu12.12-1ubuntu72.12-1ubuntu7.12.12-1ubuntu7.3 |
None known |
grub2-signedUbuntu:26.10 |
All versions, plus listed versions 1.215 |
None known |
grub2-unsignedUbuntu:26.10 |
All versions, plus listed versions 2.14-2ubuntu1 |
None known |
grub2-signedUbuntu:26.04:LTS |
All versions, plus listed versions 1.2141.215 |
None known |
grub2-unsignedUbuntu:26.04:LTS |
All versions, plus listed versions 2.14~git20250718.0e36779-1ubuntu42.14-2ubuntu1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-97876 is a medium vulnerability (CVSS 6.4) in Gnu Grub2, published October 2, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.11%, the 1st percentile. Fixed in grub 2.12-r9.
References
openwall.com/lists/oss-security/2026/09/13/5
gitlab.freedesktop.org/gnu-grub/grub/-/commit/26beaa3b2720fefdc4d04c1ae209b776fe6848d6
nvd.nist.gov/vuln/detail/CVE-2026-97876
github.com/advisories/GHSA-v555-hf4g-q6pc
docs.bell-sw.com/security/cves/CVE-2026-97876
github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97876.json
security-tracker.debian.org/tracker/CVE-2026-97876
ubuntu.com/security/CVE-2026-97876
cve.org/CVERecord?id=CVE-2026-97876