CVE-2023-34256

An issue was discovered in the Linux kernel before 6.3.3. There is an out-of-bounds read in crc16 in lib/crc16.c when called from fs/ext4/super.c because ext4_group_desc_csum does not properly check an offset. NOTE: this is disputed by third parties because the kernel is not intended to defend against attackers with the stated "When modifying the block device while it is mounted by the filesystem" access.

Published: 2023-05-31 Last update: 2025-03-11 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-34256 is rated Low Risk (22.7/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.01%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-34256

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.07% 0.01% -0.05%
2 2025-11-18 0.01% 0.07% +0.06%
3 2025-04-15 — 0.01% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-34256

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2023-34256

OS Trackers for CVE-2023-34256

vendor priority summary link
debian unimportant CVE-2023-34256 unimportant priority: Debian including 1 source packages (linux), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-34256
suse medium CVE-2023-34256 severity moderate: SUSE including 14 source package names (kernel-default, kernel-default-base, …), 236 product×package rows across 53 product lines (SUSE CaaS Platform 4.0, SUSE Enterprise Storage 7, … (53 product lines)): Known Not Affected 236. https://www.suse.com/security/cve/CVE-2023-34256/
ubuntu low CVE-2023-34256 low priority: Ubuntu including 167 source packages (linux, linux-allwinner, …), 1970 status rows across 13 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1512, released 230, not-affected 117, ignored 111. https://ubuntu.com/security/CVE-2023-34256

Affected software / configurations for CVE-2023-34256

Vendor Product Version Raw CPE
linux linux_kernel < 6.3.3 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
suse linux_enterprise 12.0 cpe:2.3:o:suse:linux_enterprise:12.0:sp5:*:*:*:*:*:*
suse linux_enterprise 15.0 cpe:2.3:o:suse:linux_enterprise:15.0:sp4:*:*:*:*:*:*
suse linux_enterprise 15.0 cpe:2.3:o:suse:linux_enterprise:15.0:sp5:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

References for CVE-2023-34256

cvelogic Threat Intelligence