CyberSecBulletin
CVE-2026-53390NVD status: Analyzed

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2026-53390 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0, 988c93d3bba066d8669143e6ec30bb2be9608d53, 36599894fa8536fefdf1e296c0af71b8b7226859 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 0.47% 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 c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0 or 988c93d3bba066d8669143e6ec30bb2be9608d53 or 36599894fa8536fefdf1e296c0af71b8b7226859 or d5c81a095c86fe507c032d08f3a8cfc518444927, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.212 or 6.6.144 or 6.12.95 or 6.18.38, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux282cbbb476b9f35793452bc461934af4c7eca169 up to, but not including, c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0; f20adc4ef7428bc485ee83fd1a592252fb87718b up to, but not including, 988c93d3bba066d8669143e6ec30bb2be9608d53; 325d4ac11f526cb8964cff14548ccf02d8c756d8 up to, but not including, 36599894fa8536fefdf1e296c0af71b8b7226859; 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c up to, but not including, d5c81a095c86fe507c032d08f3a8cfc518444927; 90089584b2e25c4510b7b987387b4405f0673ece up to, but not including, 7627ff8c4f9919f14de562b0160ab4ec9d80b1f7; d07b26f39246a82399661936dd0c853983cfade7 up to, but not including, e36e35660adb9b8ef1435ac359151dda5f094c55; d07b26f39246a82399661936dd0c853983cfade7 up to, but not including, 1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b; 151b1799861fde38087c08f613abc2843ef597b0; and 7 more rangesc7488c85fd822959e9b5c22fbd9e7c8a21caf5e0, 988c93d3bba066d8669143e6ec30bb2be9608d53, 36599894fa8536fefdf1e296c0af71b8b7226859, d5c81a095c86fe507c032d08f3a8cfc518444927, 7627ff8c4f9919f14de562b0160ab4ec9d80b1f7, e36e35660adb9b8ef1435ac359151dda5f094c55
LinuxLinux Kernel5.15.210 up to, but not including, 5.15.212; 6.6.140 up to, but not including, 6.6.144; 6.12.84 up to, but not including, 6.12.95; 6.18.25 up to, but not including, 6.18.38; 7.0.2 up to, but not including, 7.1.3; 6.1.1765.15.212, 6.6.144, 6.12.95, 6.18.38, 7.1.3

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
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:N/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: ksmbd: fix out-of-bounds read in smb_check_perm_dacl() The permission-check ACE walk in smb_check_perm_dacl() validates the ACE header size and caps sid.num_subauth at SID_MAX_SUB_AUTHORITIES, but it never checks that ace->size is actually large enough to contain num_subauth sub-authorities before compare_sids() dereferences them. CIFS_SID_BASE_SIZE covers the SID header up to but excluding the sub_auth[] array, and offsetof(struct smb_ace, sid) is the ACE header, so the existing guards only guarantee the 8-byte SID base, i.e. zero sub-authorities. compare_sids() then reads ace->sid.sub_auth[i] for i < min(local_sid->num_subauth, ace->sid.num_subauth). The local comparison SIDs (sid_everyone, sid_unix_NFS_mode, and the id_to_sid() result) always have at least one sub-authority, and an attacker controls the ACE revision and authority bytes (which lie within the in-bounds SID base), so they can match one of those SIDs and force the sub_auth read. A crafted ACE with size == 16 and num_subauth >= 1 placed at the tail of the security descriptor therefore causes a heap out-of-bounds read of up to SID_MAX_SUB_AUTHORITIES * sizeof(__le32) bytes past the pntsd allocation. The security descriptor is loaded by ksmbd_vfs_get_sd_xattr() into a buffer sized exactly to the on-disk data (kzalloc(sd_size) in ndr_decode_v4_ntacl()), so the read lands past the allocation. The malformed descriptor can be stored verbatim via SMB2_SET_INFO (the DACL is not normalised before being written to the security.NTACL xattr) and the read fires on a subsequent SMB2_CREATE access check, making this reachable by an authenticated client on a share that uses ACL xattrs. Add the missing num_subauth-versus-ace_size check, mirroring the identical guards already present in the sibling parsers parse_dacl() and smb_inherit_dacl().

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. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Read vulnerabilities

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