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Fencer Vulns
medium 5.5

CVE-2021-47238 json

net: ipv4: fix memory leak in ip_mc_add1_src

published 2024-05-21 2 y ago modified 2026-06-17 4 mo ago also EUVD-2021-33886

cvss
5.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

net: ipv4: fix memory leak in ip_mc_add1_src

BUG: memory leak unreferenced object 0xffff888101bc4c00 (size 32): comm "syz-executor527", pid 360, jiffies 4294807421 (age 19.329s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 01 00 00 00 00 00 00 00 ac 14 14 bb 00 00 02 00 ................ backtrace: [<00000000f17c5244>] kmalloc include/linux/slab.h:558 [inline] [<00000000f17c5244>] kzalloc include/linux/slab.h:688 [inline] [<00000000f17c5244>] ip_mc_add1_src net/ipv4/igmp.c:1971 [inline] [<00000000f17c5244>] ip_mc_add_src+0x95f/0xdb0 net/ipv4/igmp.c:2095 [<000000001cb99709>] ip_mc_source+0x84c/0xea0 net/ipv4/igmp.c:2416 [<0000000052cf19ed>] do_ip_setsockopt net/ipv4/ip_sockglue.c:1294 [inline] [<0000000052cf19ed>] ip_setsockopt+0x114b/0x30c0 net/ipv4/ip_sockglue.c:1423 [<00000000477edfbc>] raw_setsockopt+0x13d/0x170 net/ipv4/raw.c:857 [<00000000e75ca9bb>] __sys_setsockopt+0x158/0x270 net/socket.c:2117 [<00000000bdb993a8>] __do_sys_setsockopt net/socket.c:2128 [inline] [<00000000bdb993a8>] __se_sys_setsockopt net/socket.c:2125 [inline] [<00000000bdb993a8>] __x64_sys_setsockopt+0xba/0x150 net/socket.c:2125 [<000000006a1ffdbd>] do_syscall_64+0x40/0x80 arch/x86/entry/common.c:47 [<00000000b11467c4>] entry_SYSCALL_64_after_hwframe+0x44/0xae

In commit 24803f38a5c0 ("igmp: do not remove igmp souce list info when set link down"), the ip_mc_clear_src() in ip_mc_destroy_dev() was removed, because it was also called in igmpv3_clear_delrec().

Rough callgraph:

inetdev_destroy -> ip_mc_destroy_dev -> igmpv3_clear_delrec -> ip_mc_clear_src -> RCU_INIT_POINTER(dev->ip_ptr, NULL)

However, ip_mc_clear_src() called in igmpv3_clear_delrec() doesn't release in_dev->mc_list->sources. And RCU_INIT_POINTER() assigns the NULL to dev->ip_ptr. As a result, in_dev cannot be obtained through inetdev_by_index() and then in_dev->mc_list->sources cannot be released by ip_mc_del1_src() in the sock_close. Rough call sequence goes like:

sock_close -> __sock_release -> inet_release -> ip_mc_drop_socket -> inetdev_by_index -> ip_mc_leave_src -> ip_mc_del_src -> ip_mc_del1_src

So we still need to call ip_mc_clear_src() in ip_mc_destroy_dev() to free in_dev->mc_list->sources.

Patch / fix

  • Linux Linux 3.3, 3.17, 4.9.274, 4.14.238, 4.19.196, 5.4.128, 5.10.46, 5.12.13, 5.13
  • linux linux_kernel 0dc13e75507f, 1e28018b5c83, 3dd2aeac2e96, 6cff57eea334, 77de6ee73f54, ac31cc837caf, d8e2973029b8
  • linux Debian 14, Debian 13, Debian 12 5.10.46-1

debian advisories DEBIAN-CVE-2021-47238

  • linux Ubuntu 18.04 LTS 4.15.0-156.163
  • linux Ubuntu 20.04 LTS 5.4.0-81.91
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1111.118
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1055.58
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1051.55
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1099.101
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1045.47
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1056.58

ubuntu advisories UBUNTU-CVE-2021-47238

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.219.1
  • kernel-source SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.219.1
  • kernel-default SLES for SAP 12 SP5, SLES 12 SP5, SLE Workstation Extension 12 SP5 +2 more 4.12.14-122.219.1
  • kernel-obs-build SLE Software Development Kit 12 SP5 4.12.14-122.219.1
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.188.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.188.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.188.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.188.1

suse advisories SUSE-SU-2024:2184-1SUSE-SU-2024:1983-1SUSE-SU-2024:1979-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-47238 updated cvss 5.3

kernel: net: ipv4: fix memory leak in ip_mc_add1_src

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +6 more
    affected: workaround, no fix planned “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-selftests-internal
    affected: workaround, no fix available “Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-core, kernel-tools, python3-perf, +17 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
18 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux
  • linux linux_kernel

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.