CyberSecBulletin
CVE-2025-21735NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2025-21735 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 bd249109d266f1d52548c46634a15b71656e0d44, 674e17c5933779a8bf5c15d596fdfcb5ccdebbc2, 10b3f947b609713e04022101f492d288a014ddfa 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 0.38% 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 bd249109d266f1d52548c46634a15b71656e0d44 or 674e17c5933779a8bf5c15d596fdfcb5ccdebbc2 or 10b3f947b609713e04022101f492d288a014ddfa or d5a461c315e5ff92657f84d8ba50caa5abf5c22a, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.129 or 6.6.78 or 6.12.14 or 6.13.3, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxa1b0b9415817c14d207921582f269d03f848b69f up to, but not including, bd249109d266f1d52548c46634a15b71656e0d44; a1b0b9415817c14d207921582f269d03f848b69f up to, but not including, 674e17c5933779a8bf5c15d596fdfcb5ccdebbc2; a1b0b9415817c14d207921582f269d03f848b69f up to, but not including, 10b3f947b609713e04022101f492d288a014ddfa; a1b0b9415817c14d207921582f269d03f848b69f up to, but not including, d5a461c315e5ff92657f84d8ba50caa5abf5c22a; a1b0b9415817c14d207921582f269d03f848b69f up to, but not including, 172cdfc3a5ea20289c58fb73dadc6fd4a8784a4e; a1b0b9415817c14d207921582f269d03f848b69f up to, but not including, 2ae4bade5a64d126bd18eb66bd419005c5550218; a1b0b9415817c14d207921582f269d03f848b69f up to, but not including, 59c7ed20217c0939862fbf8145bc49d5b3a13f4f; a1b0b9415817c14d207921582f269d03f848b69f up to, but not including, 110b43ef05342d5a11284cc8b21582b698b4ef1c; and 1 more rangesbd249109d266f1d52548c46634a15b71656e0d44, 674e17c5933779a8bf5c15d596fdfcb5ccdebbc2, 10b3f947b609713e04022101f492d288a014ddfa, d5a461c315e5ff92657f84d8ba50caa5abf5c22a, 172cdfc3a5ea20289c58fb73dadc6fd4a8784a4e, 2ae4bade5a64d126bd18eb66bd419005c5550218
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
LinuxLinux Kernel4.4 up to, but not including, 6.1.129; 6.2 up to, but not including, 6.6.78; 6.7 up to, but not including, 6.12.14; 6.13 up to, but not including, 6.13.36.1.129, 6.6.78, 6.12.14, 6.13.3

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.

Scoring systemScoreSeverityScored by
CVSS 3.18.8HighCNA
CVSS 3.17.8HighNVD

Official description

In the Linux kernel, the following vulnerability has been resolved: NFC: nci: Add bounds checking in nci_hci_create_pipe() The "pipe" variable is a u8 which comes from the network. If it's more than 127, then it results in memory corruption in the caller, nci_hci_connect_gate().

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. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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