CyberSecBulletin
CVE-2025-21724NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2025-21724 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 44d9c94b7a3f29a3e07c4753603a35e9b28842a3, 38ac76fc06bc6826a3e4b12a98efbe98432380a9, d5d33f01b86af44b23eea61ee309e4ef22c0cdfe as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.19% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 44d9c94b7a3f29a3e07c4753603a35e9b28842a3 or 38ac76fc06bc6826a3e4b12a98efbe98432380a9 or d5d33f01b86af44b23eea61ee309e4ef22c0cdfe or b1f8453b8ff1ab79a03820ef608256c499769cb6, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.129 or 6.6.76 or 6.12.13 or 6.13.2, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 up to, but not including, 44d9c94b7a3f29a3e07c4753603a35e9b28842a3; 58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 up to, but not including, 38ac76fc06bc6826a3e4b12a98efbe98432380a9; 58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 up to, but not including, d5d33f01b86af44b23eea61ee309e4ef22c0cdfe; 58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 up to, but not including, b1f8453b8ff1ab79a03820ef608256c499769cb6; 58ccf0190d19d9a8a41f8a02b9e06742b58df4a1 up to, but not including, e24c1551059268b37f6f40639883eafb281b8b9c; 6.144d9c94b7a3f29a3e07c4753603a35e9b28842a3, 38ac76fc06bc6826a3e4b12a98efbe98432380a9, d5d33f01b86af44b23eea61ee309e4ef22c0cdfe, b1f8453b8ff1ab79a03820ef608256c499769cb6, e24c1551059268b37f6f40639883eafb281b8b9c
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFPV3.1.5 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFPV3.1.5 and laterNot stated
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFPV3.1.5 and laterNot stated
LinuxLinux Kernel6.1 up to, but not including, 6.1.129; 6.2 up to, but not including, 6.6.76; 6.7 up to, but not including, 6.12.13; 6.13 up to, but not including, 6.13.26.1.129, 6.6.76, 6.12.13, 6.13.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: iommufd/iova_bitmap: Fix shift-out-of-bounds in iova_bitmap_offset_to_index() Resolve a UBSAN shift-out-of-bounds issue in iova_bitmap_offset_to_index() where shifting the constant "1" (of type int) by bitmap->mapped.pgshift (an unsigned long value) could result in undefined behavior. The constant "1" defaults to a 32-bit "int", and when "pgshift" exceeds 31 (e.g., pgshift = 63) the shift operation overflows, as the result cannot be represented in a 32-bit type. To resolve this, the constant is updated to "1UL", promoting it to an unsigned long type to match the operand's type.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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