Linux: Out-of-bounds Write
CVE-2025-39935 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 cd59ca8f75dbb42a67fcae975c766114644e36c4, 78338108b5a856dc98223a335f147846a8a18c51 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 0.15% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to cd59ca8f75dbb42a67fcae975c766114644e36c4 or 78338108b5a856dc98223a335f147846a8a18c51, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.16.9 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 576c57e6b4c1d734bcb7cc33dde9a99a9383b520 up to, but not including, cd59ca8f75dbb42a67fcae975c766114644e36c4; 576c57e6b4c1d734bcb7cc33dde9a99a9383b520 up to, but not including, 78338108b5a856dc98223a335f147846a8a18c51; 6.13 | cd59ca8f75dbb42a67fcae975c766114644e36c4, 78338108b5a856dc98223a335f147846a8a18c51 |
| Linux | Linux Kernel | 6.13 up to, but not including, 6.16.9; 6.17 | 6.16.9 |
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 system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: ASoC: codec: sma1307: Fix memory corruption in sma1307_setting_loaded() The sma1307->set.header_size is how many integers are in the header (there are 8 of them) but instead of allocating space of 8 integers we allocate 8 bytes. This leads to memory corruption when we copy data it on the next line: memcpy(sma1307->set.header, data, sma1307->set.header_size * sizeof(int)); Also since we're immediately copying over the memory in ->set.header, there is no need to zero it in the allocator. Use devm_kmalloc_array() to allocate the memory instead.
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.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Out-of-bounds Write vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
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