CyberSecBulletin
CVE-2025-39735NVD status: Modified

Linux: Out-of-bounds Read

Published Updated By the CyberSecBulletin desk

CVE-2025-39735 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 7.1 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 3d6fd5b9c6acbc005e53d0211c7381f566babec1, 50afcee7011155933d8d5e8832f52eeee018cfd3, 78c9cbde8880ec02d864c166bcb4fe989ce1d95f 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 0.3% 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 3d6fd5b9c6acbc005e53d0211c7381f566babec1 or 50afcee7011155933d8d5e8832f52eeee018cfd3 or 78c9cbde8880ec02d864c166bcb4fe989ce1d95f or 46e2c031aa59ea65128991cbca474bd5c0c2ecdb, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 4.20 or 5.4.292 or 5.10.236 or 5.15.180, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux6e39b681d1eb16f408493bf5023788b57f68998c up to, but not including, 3d6fd5b9c6acbc005e53d0211c7381f566babec1; bbf3f1fd8a0ac7df1db36a9b9e923041a14369f2 up to, but not including, 50afcee7011155933d8d5e8832f52eeee018cfd3; 27a93c45e16ac25a0e2b5e5668e2d1beca56a478 up to, but not including, 78c9cbde8880ec02d864c166bcb4fe989ce1d95f; 9c356fc32a4480a2c0e537a05f2a8617633ddad0 up to, but not including, 46e2c031aa59ea65128991cbca474bd5c0c2ecdb; 9353cdf28d4c5c0ff19c5df7fbf81ea774de43a4 up to, but not including, a8c31808925b11393a6601f534bb63bac5366bab; 8c505ebeed8045b488b2e60b516c752b851f8437 up to, but not including, 0beddc2a3f9b9cf7d8887973041e36c2d0fa3652; d9f9d96136cba8fedd647d2c024342ce090133c2 up to, but not including, 16d3d36436492aa248b2d8045e75585ebcc2f34d; d9f9d96136cba8fedd647d2c024342ce090133c2 up to, but not including, 5263822558a8a7c0d0248d5679c2dcf4d5cda61f; and 12 more ranges3d6fd5b9c6acbc005e53d0211c7381f566babec1, 50afcee7011155933d8d5e8832f52eeee018cfd3, 78c9cbde8880ec02d864c166bcb4fe989ce1d95f, 46e2c031aa59ea65128991cbca474bd5c0c2ecdb, a8c31808925b11393a6601f534bb63bac5366bab, 0beddc2a3f9b9cf7d8887973041e36c2d0fa3652
LinuxLinux Kernel4.19.325 up to, but not including, 4.20; 5.4.287 up to, but not including, 5.4.292; 5.10.231 up to, but not including, 5.10.236; 5.15.174 up to, but not including, 5.15.180; 6.1.120 up to, but not including, 6.1.134; 6.6.64 up to, but not including, 6.6.87; 6.11.11 up to, but not including, 6.12; 6.12.2 up to, but not including, 6.12.23; and 2 more ranges4.20, 5.4.292, 5.10.236, 5.15.180, 6.1.134, 6.6.87

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
NoneNothing can be modified.
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:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.1HighNVD
CVSS 3.17.1HighCISA (ADP)

Official description

In the Linux kernel, the following vulnerability has been resolved: jfs: fix slab-out-of-bounds read in ea_get() During the "size_check" label in ea_get(), the code checks if the extended attribute list (xattr) size matches ea_size. If not, it logs "ea_get: invalid extended attribute" and calls print_hex_dump(). Here, EALIST_SIZE(ea_buf->xattr) returns 4110417968, which exceeds INT_MAX (2,147,483,647). Then ea_size is clamped: int size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf->xattr)); Although clamp_t aims to bound ea_size between 0 and 4110417968, the upper limit is treated as an int, causing an overflow above 2^31 - 1. This leads "size" to wrap around and become negative (-184549328). The "size" is then passed to print_hex_dump() (called "len" in print_hex_dump()), it is passed as type size_t (an unsigned type), this is then stored inside a variable called "int remaining", which is then assigned to "int linelen" which is then passed to hex_dump_to_buffer(). In print_hex_dump() the for loop, iterates through 0 to len-1, where len is 18446744073525002176, calling hex_dump_to_buffer() on each iteration: for (i = 0; i < len; i += rowsize) { linelen = min(remaining, rowsize); remaining -= rowsize; hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize, linebuf, sizeof(linebuf), ascii); ... } The expected stopping condition (i < len) is effectively broken since len is corrupted and very large. This eventually leads to the "ptr+i" being passed to hex_dump_to_buffer() to get closer to the end of the actual bounds of "ptr", eventually an out of bounds access is done in hex_dump_to_buffer() in the following for loop: for (j = 0; j < len; j++) { if (linebuflen < lx + 2) goto overflow2; ch = ptr[j]; ... } To fix this we should validate "EALIST_SIZE(ea_buf->xattr)" before it is utilised.

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. 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 Out-of-bounds Read vulnerabilities

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