How severe is CVE-2023-53503?

CVE-2023-53503 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2023-53503 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-53503?

CVE-2023-53503 primarily affects Linux Linux Kernel. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-53503?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2023-53503 have an EU (EUVD) identifier?

Yes. CVE-2023-53503 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-32776.

When was CVE-2023-53503 published?

CVE-2023-53503 was published on 2025-10-01 and last updated on 2026-06-17.

CVE-2023-53503

CVE-2023-53503 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
EPSS exploit prediction: 0% (4th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-32776
Weakness: CWE-476
Affected product: Linux Linux Kernel
Published: 2025-10-01
Last modified: 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: allow ext4_get_group_info() to fail Previously, ext4_get_group_info() would treat an invalid group number as BUG(), since in theory it should never happen. However, if a malicious attaker (or fuzzer) modifies the superblock via the block device while it is the file system is mounted, it is possible for s_first_data_block to get set to a very large number. In that case, when calculating the block group of some block number (such as the starting block of a preallocation region), could result in an underflow and very large block group number. Then the BUG_ON check in ext4_get_group_info() would fire, resutling in a denial of service attack that can be triggered by root or someone with write access to the block device. For a quality of implementation perspective, it's best that even if the system administrator does something that they shouldn't, that it will not trigger a BUG. So instead of BUG'ing, ext4_get_group_info() will call ext4_error and return NULL. We also add fallback code in all of the callers of ext4_get_group_info() that it might NULL. Also, since ext4_get_group_info() was already borderline to be an inline function, un-inline it. The results in a next reduction of the compiled text size of ext4 by roughly 2k.

Frequently asked questions

What is CVE-2023-53503?: In the Linux kernel, the following vulnerability has been resolved: ext4: allow ext4_get_group_info() to fail Previously, ext4_get_group_info() would treat an invalid group number as BUG(), since in theory it should never happen. However, if a malicious attaker (or fuzzer) modifies the superblock via the block device while it is the file system is mounted, it is possible for s_first_data_block to get set to a very large number. In that case, when calculating the block group of some block number (such as the starting block of a preallocation region), could result in an underflow and very large block group number. Then the BUG_ON check in ext4_get_group_info() would fire, resutling in a denial of service attack that can be triggered by root or someone with write access to the block device. For a quality of implementation perspective, it's best that even if the system administrator does something that they shouldn't, that it will not trigger a BUG. So instead of BUG'ing, ext4_get_group_info() will call ext4_error and return NULL. We also add fallback code in all of the callers of ext4_get_group_info() that it might NULL. Also, since ext4_get_group_info() was already borderline to be an inline function, un-inline it. The results in a next reduction of the compiled text size of ext4 by roughly 2k.
How severe is CVE-2023-53503?: CVE-2023-53503 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2023-53503 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-53503?: CVE-2023-53503 primarily affects Linux Linux Kernel. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-53503?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2023-53503 have an EU (EUVD) identifier?: Yes. CVE-2023-53503 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-32776.
When was CVE-2023-53503 published?: CVE-2023-53503 was published on 2025-10-01 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.4:rc1:*:*:*:*:*:*

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