CyberSecBulletin
CVE-2025-21680NVD status: Modified

Linux: Improper Validation of Array Index

Published Updated By the CyberSecBulletin desk

CVE-2025-21680 is a high-severity improper validation of array index 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 3450092cc2d1c311c5ea92a2486daa2a33520ea5, e5d24a7074dcd0c7e76b7e7e4efbbe7418d62486, 7cde21f52042aa2e29a654458166b873d2ae66b3 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 0.23% 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 3450092cc2d1c311c5ea92a2486daa2a33520ea5 or e5d24a7074dcd0c7e76b7e7e4efbbe7418d62486 or 7cde21f52042aa2e29a654458166b873d2ae66b3 or 1a9b65c672ca9dc4ba52ca2fd54329db9580ce29, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.177 or 6.1.127 or 6.6.74 or 6.12.11, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux52a62f8603f97e720882c8f5aff2767ac6a11d5f up to, but not including, 3450092cc2d1c311c5ea92a2486daa2a33520ea5; 52a62f8603f97e720882c8f5aff2767ac6a11d5f up to, but not including, e5d24a7074dcd0c7e76b7e7e4efbbe7418d62486; 52a62f8603f97e720882c8f5aff2767ac6a11d5f up to, but not including, 7cde21f52042aa2e29a654458166b873d2ae66b3; 52a62f8603f97e720882c8f5aff2767ac6a11d5f up to, but not including, 1a9b65c672ca9dc4ba52ca2fd54329db9580ce29; 52a62f8603f97e720882c8f5aff2767ac6a11d5f up to, but not including, 76201b5979768500bca362871db66d77cb4c225e; 5.153450092cc2d1c311c5ea92a2486daa2a33520ea5, e5d24a7074dcd0c7e76b7e7e4efbbe7418d62486, 7cde21f52042aa2e29a654458166b873d2ae66b3, 1a9b65c672ca9dc4ba52ca2fd54329db9580ce29, 76201b5979768500bca362871db66d77cb4c225e
LinuxLinux Kernel5.15 up to, but not including, 5.15.177; 5.16 up to, but not including, 6.1.127; 6.2 up to, but not including, 6.6.74; 6.7 up to, but not including, 6.12.11; 6.135.15.177, 6.1.127, 6.6.74, 6.12.11

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 3.17.8HighNVD
CVSS 3.17.8HighCISA (ADP)

Official description

In the Linux kernel, the following vulnerability has been resolved: pktgen: Avoid out-of-bounds access in get_imix_entries Passing a sufficient amount of imix entries leads to invalid access to the pkt_dev->imix_entries array because of the incorrect boundary check. UBSAN: array-index-out-of-bounds in net/core/pktgen.c:874:24 index 20 is out of range for type 'imix_pkt [20]' CPU: 2 PID: 1210 Comm: bash Not tainted 6.10.0-rc1 #121 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Call Trace: <TASK> dump_stack_lvl lib/dump_stack.c:117 __ubsan_handle_out_of_bounds lib/ubsan.c:429 get_imix_entries net/core/pktgen.c:874 pktgen_if_write net/core/pktgen.c:1063 pde_write fs/proc/inode.c:334 proc_reg_write fs/proc/inode.c:346 vfs_write fs/read_write.c:593 ksys_write fs/read_write.c:644 do_syscall_64 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe arch/x86/entry/entry_64.S:130 Found by Linux Verification Center (linuxtesting.org) with SVACE. [ fp: allow to fill the array completely; minor changelog cleanup ]

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

The underlying weakness: Improper Validation of Array Index

The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.

How developers prevent this class of flaw

  • Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, Ada allows the programmer to constrain the values of a variable and languages such as Java and Ruby will allow the programmer to handle exceptions when an out-of-bounds index is accessed.
  • Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment. For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND.

More Improper Validation of Array Index vulnerabilities (CWE-129)

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 Improper Validation of Array Index vulnerabilities

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