CyberSecBulletin
CVE-2026-53309NVD status: Analyzed

Linux: Off-by-one Error

Published Updated By the CyberSecBulletin desk

CVE-2026-53309 is a critical-severity off-by-one error 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 760ab35040aca8399021fdb9ff1db1089feb7194, c60a2710b73838d250cda57344c049b89abc5d52, 2a0673836f019e7c032acbf48d022d5ccf02a845 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 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to 760ab35040aca8399021fdb9ff1db1089feb7194 or c60a2710b73838d250cda57344c049b89abc5d52 or 2a0673836f019e7c032acbf48d022d5ccf02a845 or 819d8ebad3200a53de99bd7e297bc428e41ced54, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.258 or 5.15.209 or 6.1.175 or 6.6.141, 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
LinuxLinuxea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, 760ab35040aca8399021fdb9ff1db1089feb7194; ea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, c60a2710b73838d250cda57344c049b89abc5d52; ea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, 2a0673836f019e7c032acbf48d022d5ccf02a845; ea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, 819d8ebad3200a53de99bd7e297bc428e41ced54; ea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, d5403ae28085761d58b555645bc7d5feadb10073; ea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, 1fb7f356547d9688822315cd2b205ff0bd5429b4; ea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, 426cd8eedac89b86148d4478990eeef16e8a2520; ea2034416b54700e30371f2ad6517cbb94674083 up to, but not including, 01b61e8dda9b0fdb0d4cda43de25f4e390554d7b; and 1 more ranges760ab35040aca8399021fdb9ff1db1089feb7194, c60a2710b73838d250cda57344c049b89abc5d52, 2a0673836f019e7c032acbf48d022d5ccf02a845, 819d8ebad3200a53de99bd7e297bc428e41ced54, d5403ae28085761d58b555645bc7d5feadb10073, 1fb7f356547d9688822315cd2b205ff0bd5429b4
LinuxLinux Kernel2.6.37 up to, but not including, 5.10.258; 5.11 up to, but not including, 5.15.209; 5.16 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.91; 6.13 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.105.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33

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: ocfs2/dlm: fix off-by-one in dlm_match_regions() region comparison The local-vs-remote region comparison loop uses '<=' instead of '<', causing it to read one entry past the valid range of qr_regions. The other loops in the same function correctly use '<'. Fix the loop condition to use '<' for consistency and correctness.

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

The underlying weakness: Off-by-one Error

A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.

How developers prevent this class of flaw

  • When copying character arrays or using character manipulation methods, the correct size parameter must be used to account for the null terminator that needs to be added at the end of the array. Some examples of functions susceptible to this weakness in C include strcpy(), strncpy(), strcat(), strncat(), printf(), sprintf(), scanf() and sscanf().

More Off-by-one Error vulnerabilities (CWE-193)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Recent Off-by-one Error vulnerabilities

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