Linux: Out-of-bounds Write
CVE-2025-21927 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 3b54109b2f771f74fd53b027429796326f84ab36, 9d22cf5cc94cd7dee84773ec41db78a46107dfa3, 9fbc953d6b38bc824392e01850f0aeee3b348722 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 0.62% chance of exploitation within 30 days, higher than 50% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 3b54109b2f771f74fd53b027429796326f84ab36 or 9d22cf5cc94cd7dee84773ec41db78a46107dfa3 or 9fbc953d6b38bc824392e01850f0aeee3b348722 or 22b06c89aa6b2d1ecb8aea72edfb9d53af8d5126, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.19 or 6.13.7, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 3f2304f8c6d6ed97849057bd16fee99e434ca796 up to, but not including, 3b54109b2f771f74fd53b027429796326f84ab36; 3f2304f8c6d6ed97849057bd16fee99e434ca796 up to, but not including, 9d22cf5cc94cd7dee84773ec41db78a46107dfa3; 3f2304f8c6d6ed97849057bd16fee99e434ca796 up to, but not including, 9fbc953d6b38bc824392e01850f0aeee3b348722; 3f2304f8c6d6ed97849057bd16fee99e434ca796 up to, but not including, 22b06c89aa6b2d1ecb8aea72edfb9d53af8d5126; 3f2304f8c6d6ed97849057bd16fee99e434ca796 up to, but not including, ad95bab0cd28ed77c2c0d0b6e76e03e031391064; 5.0 | 3b54109b2f771f74fd53b027429796326f84ab36, 9d22cf5cc94cd7dee84773ec41db78a46107dfa3, 9fbc953d6b38bc824392e01850f0aeee3b348722, 22b06c89aa6b2d1ecb8aea72edfb9d53af8d5126, ad95bab0cd28ed77c2c0d0b6e76e03e031391064 |
| Linux | Linux Kernel | 5.0 up to, but not including, 6.12.19; 6.13 up to, but not including, 6.13.7; 6.14 | 6.12.19, 6.13.7 |
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 | 9.8 | Critical | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: nvme-tcp: fix potential memory corruption in nvme_tcp_recv_pdu() nvme_tcp_recv_pdu() doesn't check the validity of the header length. When header digests are enabled, a target might send a packet with an invalid header length (e.g. 255), causing nvme_tcp_verify_hdgst() to access memory outside the allocated area and cause memory corruptions by overwriting it with the calculated digest. Fix this by rejecting packets with an unexpected header length.
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.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Recent Out-of-bounds Write vulnerabilities
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 8.1 High severity
- 7.8 High severity
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