CyberSecBulletin
CVE-2025-39967NVD status: Modified

Linux: Integer Overflow or Wraparound

Published Updated By the CyberSecBulletin desk

CVE-2025-39967 is a high-severity integer overflow or wraparound 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 994bdc2d23c79087fbf7dcd9544454e8ebcef877, 9c8ec14075c5317edd6b242f1be8167aa1e4e333, b8a6e85328aeb9881531dbe89bcd2637a06c3c95 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 0.18% 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 994bdc2d23c79087fbf7dcd9544454e8ebcef877 or 9c8ec14075c5317edd6b242f1be8167aa1e4e333 or b8a6e85328aeb9881531dbe89bcd2637a06c3c95 or a6eb9f423b3db000aaedf83367b8539f6b72dcfc, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 4.5 or 4.10 or 4.15 or 4.20, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux96e41fc29e8af5c5085fb8a79cab8d0d00bab86c up to, but not including, 994bdc2d23c79087fbf7dcd9544454e8ebcef877; 39b3cffb8cf3111738ea993e2757ab382253d86a up to, but not including, 9c8ec14075c5317edd6b242f1be8167aa1e4e333; 39b3cffb8cf3111738ea993e2757ab382253d86a up to, but not including, b8a6e85328aeb9881531dbe89bcd2637a06c3c95; 39b3cffb8cf3111738ea993e2757ab382253d86a up to, but not including, a6eb9f423b3db000aaedf83367b8539f6b72dcfc; 39b3cffb8cf3111738ea993e2757ab382253d86a up to, but not including, adac90bb1aaf45ca66f9db8ac100be16750ace78; 39b3cffb8cf3111738ea993e2757ab382253d86a up to, but not including, 4a4bac869560f943edbe3c2b032062f6673b13d3; 39b3cffb8cf3111738ea993e2757ab382253d86a up to, but not including, c0c01f9aa08c8e10e10e8c9ebb5be01a4eff6eb7; 39b3cffb8cf3111738ea993e2757ab382253d86a up to, but not including, 1a194e6c8e1ee745e914b0b7f50fa86c89ed13fe; and 12 more ranges994bdc2d23c79087fbf7dcd9544454e8ebcef877, 9c8ec14075c5317edd6b242f1be8167aa1e4e333, b8a6e85328aeb9881531dbe89bcd2637a06c3c95, a6eb9f423b3db000aaedf83367b8539f6b72dcfc, adac90bb1aaf45ca66f9db8ac100be16750ace78, 4a4bac869560f943edbe3c2b032062f6673b13d3
LinuxLinux Kernel4.4.235 up to, but not including, 4.5; 4.9.235 up to, but not including, 4.10; 4.14.196 up to, but not including, 4.15; 4.19.143 up to, but not including, 4.20; 5.4.62 up to, but not including, 5.4.300; 5.8.6 up to, but not including, 5.9; 5.9.1 up to, but not including, 5.10.245; 5.11 up to, but not including, 5.15.194; and 6 more ranges4.5, 4.10, 4.15, 4.20, 5.4.300, 5.9

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 3.17.8HighCNA
CVSS 3.17.8HighNVD

Official description

In the Linux kernel, the following vulnerability has been resolved: fbcon: fix integer overflow in fbcon_do_set_font Fix integer overflow vulnerabilities in fbcon_do_set_font() where font size calculations could overflow when handling user-controlled font parameters. The vulnerabilities occur when: 1. CALC_FONTSZ(h, pitch, charcount) performs h * pith * charcount multiplication with user-controlled values that can overflow. 2. FONT_EXTRA_WORDS * sizeof(int) + size addition can also overflow 3. This results in smaller allocations than expected, leading to buffer overflows during font data copying. Add explicit overflow checking using check_mul_overflow() and check_add_overflow() kernel helpers to safety validate all size calculations before allocation.

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

The underlying weakness: Integer Overflow or Wraparound

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

How developers prevent this class of flaw

  • Ensure that all protocols are strictly defined, such that all out-of-bounds behavior can be identified simply, and require strict conformance to the protocol.
  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. If possible, choose a language or compiler that performs automatic bounds checking.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Use libraries or frameworks that make it easier to handle numbers without unexpected consequences. Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).

More Integer Overflow or Wraparound vulnerabilities (CWE-190)

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 Integer Overflow or Wraparound vulnerabilities

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