5.5

CVE-2021-47363: nexthop: Fix division by zero while replacing a resilient group

Analyzed
AliasesUBUNTU-CVE-2021-47363DEBIAN-CVE-2021-47363
Published 21-05-2024Last modified 11-05-2026

Vulnerability summary

CVE-2021-47363 is a medium (CVSS 5.5) Divide By Zero vulnerability in linux. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 10.9% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.21%
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 5 · Related 5
SUSE-SU-2024:2008-1SUSE-SU-2024:2011-1SUSE-SU-2024:2019-1SUSE-SU-2024:2189-1SUSE-SU-2024:2190-1

Timeline

  1. 21-05-2024
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: nexthop: Fix division by zero while replacing a resilient group The resilient nexthop group torture tests in fib_nexthop.sh exposed a possible division by zero while replacing a resilient group [1]. The division by zero occurs when the data path sees a resilient nexthop group with zero buckets. The tests replace a resilient nexthop group in a loop while traffic is forwarded through it. The tests do not specify the number of buckets while performing the replacement, resulting in the kernel allocating a stub resilient table (i.e, 'struct nh_res_table') with zero buckets. This table should never be visible to the data path, but the old nexthop group (i.e., 'oldg') might still be used by the data path when the stub table is assigned to it. Fix this by only assigning the stub table to the old nexthop group after making sure the group is no longer used by the data path. Tested with fib_nexthops.sh: Tests passed: 222 Tests failed: 0 [1] divide error: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 1850 Comm: ping Not tainted 5.14.0-custom-10271-ga86eb53057fe #1107 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014 RIP: 0010:nexthop_select_path+0x2d2/0x1a80 [...] Call Trace: fib_select_multipath+0x79b/0x1530 fib_select_path+0x8fb/0x1c10 ip_route_output_key_hash_rcu+0x1198/0x2da0 ip_route_output_key_hash+0x190/0x340 ip_route_output_flow+0x21/0x120 raw_sendmsg+0x91d/0x2e10 inet_sendmsg+0x9e/0xe0 __sys_sendto+0x23d/0x360 __x64_sys_sendto+0xe1/0x1b0 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.21%

Chance of exploitation in the next 30 days

Percentile

11%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.21% 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.

Ubuntu62 products
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
  • linux-aws-5.13All versions (No fix recorded)
  • linux-aws-5.19All versions (No fix recorded)
Linux2 products
  • linux≥ 283a72a5599e80750699d2021830a294ed9ab3f3, < e9d32ec26e7f01d1af13bdc687f586362546aa25 | ≥ 283a72a5599e80750699d2021830a294ed9ab3f3, < 563f23b002534176f49524b5ca0e1d94d8906c40 | 5.13
  • linux_kernel≥ 5.13, < 5.14.9 | 5.15:rc1 | 5.15:rc2
Debian1 product
  • linux< 5.14.9-1

3 vendors · 65 products

References

6 links