CyberSecBulletin
CVE-2024-49996NVD status: Modified

Linux: Buffer Copy without Checking Size of Input

Published Updated By the CyberSecBulletin desk

CVE-2024-49996 is a high-severity buffer copy without checking size of input 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 7b222d6cb87077faf56a687a72af1951cf78c8a9, 73b078e3314d4854fd8286f3ba65c860ddd3a3dd, 01cdddde39b065074fd48f07027757783cbf5b7d 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 0.79% chance of exploitation within 30 days, higher than 57% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 7b222d6cb87077faf56a687a72af1951cf78c8a9 or 73b078e3314d4854fd8286f3ba65c860ddd3a3dd or 01cdddde39b065074fd48f07027757783cbf5b7d or ec79e6170bcae8a6036a4b6960f5e7e59a785601, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.4.287 or 5.10.231 or 5.15.174 or 6.1.120, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxd5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, 7b222d6cb87077faf56a687a72af1951cf78c8a9; d5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, 73b078e3314d4854fd8286f3ba65c860ddd3a3dd; d5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, 01cdddde39b065074fd48f07027757783cbf5b7d; d5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, ec79e6170bcae8a6036a4b6960f5e7e59a785601; d5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, c6db81c550cea0c73bd72ef55f579991e0e4ba07; d5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, 803b3a39cb096d8718c0aebc03fd19f11c7dc919; d5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, c173d47b69f07cd7ca08efb4e458adbd4725d8e9; d5ecebc4900df7f6e8dff0717574668885110553 up to, but not including, e2a8910af01653c1c268984855629d71fb81f404; and 1 more ranges7b222d6cb87077faf56a687a72af1951cf78c8a9, 73b078e3314d4854fd8286f3ba65c860ddd3a3dd, 01cdddde39b065074fd48f07027757783cbf5b7d, ec79e6170bcae8a6036a4b6960f5e7e59a785601, c6db81c550cea0c73bd72ef55f579991e0e4ba07, 803b3a39cb096d8718c0aebc03fd19f11c7dc919
DebianDebian Linux11.0Not stated
LinuxLinux Kernel5.3 up to, but not including, 5.4.287; 5.5 up to, but not including, 5.10.231; 5.11 up to, but not including, 5.15.174; 5.16 up to, but not including, 6.1.120; 6.2 up to, but not including, 6.6.55; 6.7 up to, but not including, 6.10.14; 6.11 up to, but not including, 6.11.35.4.287, 5.10.231, 5.15.174, 6.1.120, 6.6.55, 6.10.14

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
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 NVD.

Scoring systemScoreSeverityScored by
CVSS 3.19.4CriticalCNA
CVSS 3.17.8HighNVD

Official description

In the Linux kernel, the following vulnerability has been resolved: cifs: Fix buffer overflow when parsing NFS reparse points ReparseDataLength is sum of the InodeType size and DataBuffer size. So to get DataBuffer size it is needed to subtract InodeType's size from ReparseDataLength. Function cifs_strndup_from_utf16() is currentlly accessing buf->DataBuffer at position after the end of the buffer because it does not subtract InodeType size from the length. Fix this problem and correctly subtract variable len. Member InodeType is present only when reparse buffer is large enough. Check for ReparseDataLength before accessing InodeType to prevent another invalid memory access. Major and minor rdev values are present also only when reparse buffer is large enough. Check for reparse buffer size before calling reparse_mkdev().

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

The underlying weakness: Buffer Copy without Checking Size of Input

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output 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 Buffer Copy without Checking Size of Input vulnerabilities (CWE-120)

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

Third-party and government advisories

Recent Buffer Copy without Checking Size of Input vulnerabilities

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