CyberSecBulletin
CVE-2026-53366NVD status: Modified

Linux: Incorrect Calculation of Buffer Size

Published Updated By the CyberSecBulletin desk

CVE-2026-53366 is a high-severity incorrect calculation of buffer size 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 5c6375bced6147ec2e460ee3b653f4860d5ecdc2, ce494707a9c07f27c219ca67f3e138061f53d9b3, a9c24eda24bd15f432e37824e6fc440977cb241c 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 0.17% 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 5c6375bced6147ec2e460ee3b653f4860d5ecdc2 or ce494707a9c07f27c219ca67f3e138061f53d9b3 or a9c24eda24bd15f432e37824e6fc440977cb241c or 77798d7be6ef71e72fb6fc8a2901bf74ebc9706f, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.144 or 6.12.95 or 6.18.38 or 7.1.3, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux8eb77cc73977d88787b37c92831b1c242e035396 up to, but not including, 5c6375bced6147ec2e460ee3b653f4860d5ecdc2; 8eb77cc73977d88787b37c92831b1c242e035396 up to, but not including, ce494707a9c07f27c219ca67f3e138061f53d9b3; 8eb77cc73977d88787b37c92831b1c242e035396 up to, but not including, a9c24eda24bd15f432e37824e6fc440977cb241c; 8eb77cc73977d88787b37c92831b1c242e035396 up to, but not including, 77798d7be6ef71e72fb6fc8a2901bf74ebc9706f; 8eb77cc73977d88787b37c92831b1c242e035396 up to, but not including, c04d9ece23deb9e26c19f9ca215e98b3295aa1bb; 8eb77cc73977d88787b37c92831b1c242e035396 up to, but not including, eca856950f7cb1a221e02b99d758409f2c5cec42; 6.05c6375bced6147ec2e460ee3b653f4860d5ecdc2, ce494707a9c07f27c219ca67f3e138061f53d9b3, a9c24eda24bd15f432e37824e6fc440977cb241c, 77798d7be6ef71e72fb6fc8a2901bf74ebc9706f, c04d9ece23deb9e26c19f9ca215e98b3295aa1bb, eca856950f7cb1a221e02b99d758409f2c5cec42
LinuxLinux Kernel6.0 up to, but not including, 6.6.144; 6.7 up to, but not including, 6.12.95; 6.13 up to, but not including, 6.18.38; 6.19 up to, but not including, 7.1.36.6.144, 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
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: ipv4: account for fraggap on the paged allocation path In __ip_append_data(), when the paged-allocation branch is taken, alloclen and pagedlen are computed as alloclen = fragheaderlen + transhdrlen; pagedlen = datalen - transhdrlen; datalen already includes fraggap, but the fraggap bytes carried over from the previous skb are copied into the new skb's linear area at offset transhdrlen by the subsequent skb_copy_and_csum_bits(). The linear area is therefore undersized by fraggap bytes while pagedlen is overstated by the same amount. The non-paged branch sets alloclen to fraglen, which already accounts for fraggap because datalen does. Bring the paged branch in line by adding fraggap to alloclen and subtracting it from pagedlen. After this adjustment, copy no longer collapses to -fraggap on the paged path, so remove the stale comment describing that old arithmetic.

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

The underlying weakness: Incorrect Calculation of Buffer Size

The product does not correctly calculate the size to be used when allocating a buffer.

How developers prevent this class of flaw

  • When allocating a buffer for the purpose of transforming, converting, or encoding an input, allocate enough memory to handle the largest possible encoding. For example, in a routine that converts & characters to & for HTML entity encoding, the output buffer needs to be at least 5 times as large as the input buffer.
  • Understand the programming language's underlying representation and how it interacts with numeric calculation (CWE-681). Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, not-a-number calculations, and how the language handles numbers that are too large or too small for its underlying representation. Also be careful to account for 32-bit, 64-bit, and other potential differences that may affect the numeric representation.
  • Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.

More Incorrect Calculation of Buffer Size vulnerabilities (CWE-131)

Timeline

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

References

Recent Incorrect Calculation of Buffer Size vulnerabilities

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