CyberSecBulletin
CVE-2026-64268NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-64268 is a critical-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions a31b6d18ded3cc32d9ee85a6ff0726d4274887b2, 595e6537ad1a210da32cbb9a7f91aa73090915ba, 3ef7e052cbd05a8b13a51a07b185a39ec93ee1cf 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 0.71% chance of exploitation within 30 days, higher than 54% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to a31b6d18ded3cc32d9ee85a6ff0726d4274887b2 or 595e6537ad1a210da32cbb9a7f91aa73090915ba or 3ef7e052cbd05a8b13a51a07b185a39ec93ee1cf or b2e26c955f8dd7e8d3f16c858db05245ea4fa817, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.261 or 5.15.212 or 6.1.178 or 6.6.145, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, a31b6d18ded3cc32d9ee85a6ff0726d4274887b2; 8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, 595e6537ad1a210da32cbb9a7f91aa73090915ba; 8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, 3ef7e052cbd05a8b13a51a07b185a39ec93ee1cf; 8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, b2e26c955f8dd7e8d3f16c858db05245ea4fa817; 8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, 6bc89f34a4597f9f6d41f7a60c67a3153bfe8851; 8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, 423a78ff7928c2601013f73ec6d896f5597d0df5; 8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, 75c93cd3c421890f49ea93f0b978b9b7bb10e5e3; 8b6a361b8c482f22ac99c3273285ff16b23fba91 up to, but not including, 7d29f7e9dbd844cae4d3e559cf78324b9642fd6b; and 1 more rangesa31b6d18ded3cc32d9ee85a6ff0726d4274887b2, 595e6537ad1a210da32cbb9a7f91aa73090915ba, 3ef7e052cbd05a8b13a51a07b185a39ec93ee1cf, b2e26c955f8dd7e8d3f16c858db05245ea4fa817, 6bc89f34a4597f9f6d41f7a60c67a3153bfe8851, 423a78ff7928c2601013f73ec6d896f5597d0df5
LinuxLinux Kernel5.3 up to, but not including, 5.10.261; 5.11 up to, but not including, 5.15.212; 5.16 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.45.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39

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
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
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:N/AC:L/PR:N/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: RDMA/siw: bound Read Response placement to the RREAD length In drivers/infiniband/sw/siw/siw_qp_rx.c, siw_proc_rresp() places each inbound Read Response DDP segment at sge->laddr + wqe->processed and then accumulates wqe->processed, but it never checks the running total against the sink buffer length on continuation segments. siw_check_sge() resolves and validates the sink memory only on the first fragment (the if (!*mem) branch), and siw_rresp_check_ntoh() compares the cumulative length against wqe->bytes only on the final segment (the !frx->more_ddp_segs guard). A connected siw peer that answers an outstanding RREAD with Read Response segments that keep the DDP Last flag clear, carrying more total payload than the RREAD requested, drives wqe->processed past the validated sink buffer; the next siw_rx_data() call writes out of bounds at sge->laddr + wqe->processed. siw runs iWARP over ordinary routable TCP, so the peer is the remote end of an established RDMA connection and needs no local privilege. Bound every segment before placement, exactly as siw_proc_send() and siw_proc_write() already do for their tagged and untagged paths, and terminate the connection with a base-or-bounds DDP error when the Read Response would overrun the sink buffer. This is the second receive-path length fix for this file. A separate change rejects an MPA FPDU length that underflows the per-fragment remainder in the header decode; that guard does not cover this case, because here each individual segment length is self-consistent and only the accumulated placement offset overruns the buffer.

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: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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