CyberSecBulletin
CVE-2026-45856NVD status: Modified

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-45856 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.1 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 9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7, 9b5ac1c15334d46c0dbd49d64a2257b929500163, 01c9b152647dc70dc06a4a2eff86ebb3b3c76075 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 0.19% 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 9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7 or 9b5ac1c15334d46c0dbd49d64a2257b929500163 or 01c9b152647dc70dc06a4a2eff86ebb3b3c76075 or bf1feed1a7886af945f92890493aefd2b5c9928a, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.252 or 5.15.202 or 6.1.165 or 6.6.128, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxc3bea3d2dc5358e05541527283279102383b0231 up to, but not including, 9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7; c3bea3d2dc5358e05541527283279102383b0231 up to, but not including, 9b5ac1c15334d46c0dbd49d64a2257b929500163; c3bea3d2dc5358e05541527283279102383b0231 up to, but not including, 01c9b152647dc70dc06a4a2eff86ebb3b3c76075; c3bea3d2dc5358e05541527283279102383b0231 up to, but not including, bf1feed1a7886af945f92890493aefd2b5c9928a; c3bea3d2dc5358e05541527283279102383b0231 up to, but not including, d533425ac1f2925b4fc3e4ed9b9d72362cb23475; c3bea3d2dc5358e05541527283279102383b0231 up to, but not including, bf4454da8b1e712714628c0a0d6e7845bb40790a; c3bea3d2dc5358e05541527283279102383b0231 up to, but not including, bef70ff9841990658610512b4a18e4a88c9b4df6; c3bea3d2dc5358e05541527283279102383b0231 up to, but not including, 1956f0a74ccf5dc9c3ef717f2985c3ed3400aab0; and 1 more ranges9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7, 9b5ac1c15334d46c0dbd49d64a2257b929500163, 01c9b152647dc70dc06a4a2eff86ebb3b3c76075, bf1feed1a7886af945f92890493aefd2b5c9928a, d533425ac1f2925b4fc3e4ed9b9d72362cb23475, bf4454da8b1e712714628c0a0d6e7845bb40790a
LinuxLinux Kernel5.0 up to, but not including, 5.10.252; 5.11 up to, but not including, 5.15.202; 5.16 up to, but not including, 6.1.165; 6.2 up to, but not including, 6.6.128; 6.7 up to, but not including, 6.12.75; 6.13 up to, but not including, 6.18.14; 6.19 up to, but not including, 6.19.45.10.252, 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.14

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
NoneNothing can be modified.
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:N/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: RDMA/uverbs: Validate wqe_size before using it in ib_uverbs_post_send ib_uverbs_post_send() uses cmd.wqe_size from userspace without any validation before passing it to kmalloc() and using the allocated buffer as struct ib_uverbs_send_wr. If a user provides a small wqe_size value (e.g., 1), kmalloc() will succeed, but subsequent accesses to user_wr->opcode, user_wr->num_sge, and other fields will read beyond the allocated buffer, resulting in an out-of-bounds read from kernel heap memory. This could potentially leak sensitive kernel information to userspace. Additionally, providing an excessively large wqe_size can trigger a WARNING in the memory allocation path, as reported by syzkaller. This is inconsistent with ib_uverbs_unmarshall_recv() which properly validates that wqe_size >= sizeof(struct ib_uverbs_recv_wr) before proceeding. Add the same validation for ib_uverbs_post_send() to ensure wqe_size is at least sizeof(struct ib_uverbs_send_wr).

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Read

The product reads data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that provides appropriate memory abstractions.

More Out-of-bounds Read vulnerabilities (CWE-125)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Read vulnerabilities

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