Linux: Out-of-bounds Write
CVE-2026-63987 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 d4c9cc7c47781c6f4fa29d80a1193a8bcd1525bc, 0c02c190bcd9822477038ff2cee10ea584ac1b1d, 6205f7166d2dd14a017a5802c81e5bd1421a8635 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 0.13% 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 d4c9cc7c47781c6f4fa29d80a1193a8bcd1525bc or 0c02c190bcd9822477038ff2cee10ea584ac1b1d or 6205f7166d2dd14a017a5802c81e5bd1421a8635 or 7281b096b072f6c6e30420e3467d738f2e4c4b57, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.93 or 6.18.35 or 7.0.12, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | f750dfe825b904164688adeb147950e0e0c4d262 up to, but not including, d4c9cc7c47781c6f4fa29d80a1193a8bcd1525bc; f750dfe825b904164688adeb147950e0e0c4d262 up to, but not including, 0c02c190bcd9822477038ff2cee10ea584ac1b1d; f750dfe825b904164688adeb147950e0e0c4d262 up to, but not including, 6205f7166d2dd14a017a5802c81e5bd1421a8635; f750dfe825b904164688adeb147950e0e0c4d262 up to, but not including, 7281b096b072f6c6e30420e3467d738f2e4c4b57; 6.11 | d4c9cc7c47781c6f4fa29d80a1193a8bcd1525bc, 0c02c190bcd9822477038ff2cee10ea584ac1b1d, 6205f7166d2dd14a017a5802c81e5bd1421a8635, 7281b096b072f6c6e30420e3467d738f2e4c4b57 |
| Linux | Linux Kernel | 6.11 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.1 | 6.12.93, 6.18.35, 7.0.12 |
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 CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: ethtool: coalesce: cap profile updates at NET_DIM_PARAMS_NUM_PROFILES ethnl_update_profile() walks the ETHTOOL_A_PROFILE_IRQ_MODERATION nest list with an index 'i' and writes new_profile[i++] without bounding i. The destination is kmemdup()'d at NET_DIM_PARAMS_NUM_PROFILES entries (5), but the Netlink nest count is entirely user-controlled. Netlink policies do not have support for constraining the number of nested entries (or number of multi-attr entries).
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
Recent Out-of-bounds Write vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 8.4 High severity
- 7.8 High severity
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