Linux: Improper Validation of Array Index
CVE-2025-21692 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 03c56665dab1f4ac844bc156652d50d639093fa5, bcf0d815e728a3a304b50455b32a3170c16e1eaa, 1332c6ed446be787f901ed1064ec6a3c694f028a 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 0.62% chance of exploitation within 30 days, higher than 50% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 03c56665dab1f4ac844bc156652d50d639093fa5 or bcf0d815e728a3a304b50455b32a3170c16e1eaa or 1332c6ed446be787f901ed1064ec6a3c694f028a or f4168299e553f17aa2ba4016e77a9c38da40eb1d, whichever matches your release line, or a later version.
- Update RUGGEDCOM RST2428P to V3.2 or a later version.
- Update SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family to V3.2 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33 up to, but not including, 03c56665dab1f4ac844bc156652d50d639093fa5; dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33 up to, but not including, bcf0d815e728a3a304b50455b32a3170c16e1eaa; dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33 up to, but not including, 1332c6ed446be787f901ed1064ec6a3c694f028a; dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33 up to, but not including, f4168299e553f17aa2ba4016e77a9c38da40eb1d; dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33 up to, but not including, 997f6ec4208b23c87daf9f044689685f091826f7; dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33 up to, but not including, f6b0f05fbfa4044f890e8a348288c0d9a20bd1d0; dcc68b4d8084e1ac9af0d4022d6b1aff6a139a33 up to, but not including, d62b04fca4340a0d468d7853bd66e511935a18cb; 5.6 | 03c56665dab1f4ac844bc156652d50d639093fa5, bcf0d815e728a3a304b50455b32a3170c16e1eaa, 1332c6ed446be787f901ed1064ec6a3c694f028a, f4168299e553f17aa2ba4016e77a9c38da40eb1d, 997f6ec4208b23c87daf9f044689685f091826f7, f6b0f05fbfa4044f890e8a348288c0d9a20bd1d0 |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Siemens | RUGGEDCOM RST2428P | before V3.2 | V3.2 |
| Siemens | SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family | before V3.2 | V3.2 |
| Siemens | SCALANCE XCM-/XRM-/XCH-/XRH-300 family | before V3.2 | V3.2 |
| Linux | Linux Kernel | 5.6 up to, but not including, 5.10.234; 5.11 up to, but not including, 5.15.178; 5.16 up to, but not including, 6.1.128; 6.2 up to, but not including, 6.6.75; 6.7 up to, but not including, 6.12.12; 6.13 | 5.10.234, 5.15.178, 6.1.128, 6.6.75, 6.12.12 |
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 system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: net: sched: fix ets qdisc OOB Indexing Haowei Yan <[email protected]> found that ets_class_from_arg() can index an Out-Of-Bound class in ets_class_from_arg() when passed clid of 0. The overflow may cause local privilege escalation. [ 18.852298] ------------[ cut here ]------------ [ 18.853271] UBSAN: array-index-out-of-bounds in net/sched/sch_ets.c:93:20 [ 18.853743] index 18446744073709551615 is out of range for type 'ets_class [16]' [ 18.854254] CPU: 0 UID: 0 PID: 1275 Comm: poc Not tainted 6.12.6-dirty #17 [ 18.854821] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 [ 18.856532] Call Trace: [ 18.857441] <TASK> [ 18.858227] dump_stack_lvl+0xc2/0xf0 [ 18.859607] dump_stack+0x10/0x20 [ 18.860908] __ubsan_handle_out_of_bounds+0xa7/0xf0 [ 18.864022] ets_class_change+0x3d6/0x3f0 [ 18.864322] tc_ctl_tclass+0x251/0x910 [ 18.864587] ? lock_acquire+0x5e/0x140 [ 18.865113] ? __mutex_lock+0x9c/0xe70 [ 18.866009] ? __mutex_lock+0xa34/0xe70 [ 18.866401] rtnetlink_rcv_msg+0x170/0x6f0 [ 18.866806] ? __lock_acquire+0x578/0xc10 [ 18.867184] ? __pfx_rtnetlink_rcv_msg+0x10/0x10 [ 18.867503] netlink_rcv_skb+0x59/0x110 [ 18.867776] rtnetlink_rcv+0x15/0x30 [ 18.868159] netlink_unicast+0x1c3/0x2b0 [ 18.868440] netlink_sendmsg+0x239/0x4b0 [ 18.868721] ____sys_sendmsg+0x3e2/0x410 [ 18.869012] ___sys_sendmsg+0x88/0xe0 [ 18.869276] ? rseq_ip_fixup+0x198/0x260 [ 18.869563] ? rseq_update_cpu_node_id+0x10a/0x190 [ 18.869900] ? trace_hardirqs_off+0x5a/0xd0 [ 18.870196] ? syscall_exit_to_user_mode+0xcc/0x220 [ 18.870547] ? do_syscall_64+0x93/0x150 [ 18.870821] ? __memcg_slab_free_hook+0x69/0x290 [ 18.871157] __sys_sendmsg+0x69/0xd0 [ 18.871416] __x64_sys_sendmsg+0x1d/0x30 [ 18.871699] x64_sys_call+0x9e2/0x2670 [ 18.871979] do_syscall_64+0x87/0x150 [ 18.873280] ? do_syscall_64+0x93/0x150 [ 18.874742] ? lock_release+0x7b/0x160 [ 18.876157] ? do_user_addr_fault+0x5ce/0x8f0 [ 18.877833] ? irqentry_exit_to_user_mode+0xc2/0x210 [ 18.879608] ? irqentry_exit+0x77/0xb0 [ 18.879808] ? clear_bhb_loop+0x15/0x70 [ 18.880023] ? clear_bhb_loop+0x15/0x70 [ 18.880223] ? clear_bhb_loop+0x15/0x70 [ 18.880426] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 18.880683] RIP: 0033:0x44a957 [ 18.880851] Code: ff ff e8 fc 00 00 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 8974 24 10 [ 18.881766] RSP: 002b:00007ffcdd00fad8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 18.882149] RAX: ffffffffffffffda RBX: 00007ffcdd010db8 RCX: 000000000044a957 [ 18.882507] RDX: 0000000000000000 RSI: 00007ffcdd00fb70 RDI: 0000000000000003 [ 18.885037] RBP: 00007ffcdd010bc0 R08: 000000000703c770 R09: 000000000703c7c0 [ 18.887203] R10: 0000000000000080 R11: 0000000000000246 R12: 0000000000000001 [ 18.888026] R13: 00007ffcdd010da8 R14: 00000000004ca7d0 R15: 0000000000000001 [ 18.888395] </TASK> [ 18.888610] ---[ end trace ]---
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
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/03c56665dab1f4ac844bc156652d50d639093fa5
- git.kernel.org/stable/c/1332c6ed446be787f901ed1064ec6a3c694f028a
- git.kernel.org/stable/c/997f6ec4208b23c87daf9f044689685f091826f7
- git.kernel.org/stable/c/bcf0d815e728a3a304b50455b32a3170c16e1eaa
- git.kernel.org/stable/c/d62b04fca4340a0d468d7853bd66e511935a18cb
- git.kernel.org/stable/c/f4168299e553f17aa2ba4016e77a9c38da40eb1d
- git.kernel.org/stable/c/f6b0f05fbfa4044f890e8a348288c0d9a20bd1d0
Other references
Recent Improper Validation of Array Index vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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