7.8

CVE-2021-4439: isdn: cpai: check ctr->cnr to avoid array index out of bound

Modified
AliasesUBUNTU-CVE-2021-4439DEBIAN-CVE-2021-4439
Published 20-06-2024Last modified 11-05-2026

Vulnerability summary

CVE-2021-4439 is a high (CVSS 7.8) Improper Validation of Array Index vulnerability in linux. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14.5% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
7.8/10
010
High · v3.1 (NVD)
EPSS score
0.24%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 12 · Related 12
SUSE-SU-2024:2360-1SUSE-SU-2024:2362-1SUSE-SU-2024:2365-1SUSE-SU-2024:2372-1SUSE-SU-2024:2381-1SUSE-SU-2024:2384-1

Timeline

  1. 20-06-2024
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: isdn: cpai: check ctr->cnr to avoid array index out of bound The cmtp_add_connection() would add a cmtp session to a controller and run a kernel thread to process cmtp. __module_get(THIS_MODULE); session->task = kthread_run(cmtp_session, session, "kcmtpd_ctr_%d", session->num); During this process, the kernel thread would call detach_capi_ctr() to detach a register controller. if the controller was not attached yet, detach_capi_ctr() would trigger an array-index-out-bounds bug. [ 46.866069][ T6479] UBSAN: array-index-out-of-bounds in drivers/isdn/capi/kcapi.c:483:21 [ 46.867196][ T6479] index -1 is out of range for type 'capi_ctr *[32]' [ 46.867982][ T6479] CPU: 1 PID: 6479 Comm: kcmtpd_ctr_0 Not tainted 5.15.0-rc2+ #8 [ 46.869002][ T6479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 46.870107][ T6479] Call Trace: [ 46.870473][ T6479] dump_stack_lvl+0x57/0x7d [ 46.870974][ T6479] ubsan_epilogue+0x5/0x40 [ 46.871458][ T6479] __ubsan_handle_out_of_bounds.cold+0x43/0x48 [ 46.872135][ T6479] detach_capi_ctr+0x64/0xc0 [ 46.872639][ T6479] cmtp_session+0x5c8/0x5d0 [ 46.873131][ T6479] ? __init_waitqueue_head+0x60/0x60 [ 46.873712][ T6479] ? cmtp_add_msgpart+0x120/0x120 [ 46.874256][ T6479] kthread+0x147/0x170 [ 46.874709][ T6479] ? set_kthread_struct+0x40/0x40 [ 46.875248][ T6479] ret_from_fork+0x1f/0x30 [ 46.875773][ T6479]

CVSS metrics

4 scores · 3 sources · 2 versions

EPSS trend

Probability

0.24%

Chance of exploitation in the next 30 days

Percentile

15%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.24% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu88 products
  • linuxAll versions (No fix recorded) | < 4.4.0-222.255 | < 4.15.0-166.174 | < 5.4.0-92.103
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 4.4.0-1102.107 | < 4.4.0-1138.152 | < 4.15.0-1118.125 | < 5.4.0-1061.64
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < e8b8de17e164c9f1b7777f1c6f99d05539000036 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 24219a977bfe3d658687e45615c70998acdbac5a | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 9b6b2db77bc3121fe435f1d4b56e34de443bec75 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 7d91adc0ccb060ce564103315189466eb822cc6a | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 285e9210b1fab96a11c0be3ed5cea9dd48b6ac54 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 7f221ccbee4ec662e2292d490a43ce6c314c4594 | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < cc20226e218a2375d50dd9ac14fb4121b43375ff | ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 1f3e2e97c003f80c4b087092b225c8787ff91e4d | 2.6.12
  • linux_kernel< 4.4.290 | ≥ 4.5, < 4.9.288 | ≥ 4.10, < 4.14.253 | ≥ 4.15, < 4.19.214 | ≥ 4.20, < 5.4.156 | ≥ 5.5, < 5.10.76 | ≥ 5.11, < 5.14.15 | 5.15:rc1 | 5.15:rc2 | 5.15:rc3 | 5.15:rc4 | 5.15:rc5
Debian1 product
  • linux< 5.14.16-1

3 vendors · 91 products

References

12 links
Show all 12 references