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CVE Record

CVE-2021-47238: net: ipv4: fix memory leak in ip_mc_add1_src

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.

MediumCVSS 5.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

A local user or process can trigger a Linux kernel memory leak in IPv4 multicast source handling. Repeated abuse could consume kernel memory and reduce availability. The published CVSS rates impact only availability, not data theft or tampering. This is mainly a patching and exposure-control issue for systems that allow untrusted local code.

Executive priority

Schedule remediation through normal vulnerability management, with higher urgency for shared Linux systems. The issue is not remotely exploitable per CVSS, but availability impact can matter on dense or multi-tenant infrastructure.

Technical view

The flaw is a CWE-400 resource-management bug in ip_mc_add1_src and IGMP cleanup. A prior change removed ip_mc_clear_src() from ip_mc_destroy_dev(), leaving in_dev->mc_list->sources unreleased after device destruction and preventing later socket-close cleanup. Kernel stable fixes restore cleanup so multicast source entries are freed.

Likely exposure

Exposure is local: CVSS AV:L/PR:L indicates an attacker needs local privileges or a local process context. Linux systems running affected kernel builds in the listed 4.9, 4.14, 4.19, 5.4, 5.10, 5.12, and 5.13 lines may be affected until updated with the relevant stable fix.

Exploitation context

The source bundle shows syzkaller-style discovery evidence and a kernel memory leak backtrace. It does not state public exploitation, exploitation in the wild, or KEV listing. Treat active exploitation as unproven based on the provided sources.

Researcher notes

Focus validation on affected kernel lineage and vendor backport status. The vulnerability path involves IPv4 multicast source management, device teardown, and socket close cleanup. The provided evidence supports availability risk from memory leakage, not confidentiality or integrity impact.

Mitigation direction

  • Update affected Linux kernels to a vendor build containing the listed stable fixes.
  • Prioritize multi-user hosts, container hosts, and systems running untrusted local workloads.
  • Check distribution advisories for backported fixes and supported kernel package versions.
  • Reduce untrusted local shell or workload access where patching is delayed.

Validation and detection

  • Inventory Linux kernel versions across servers, endpoints, appliances, and container hosts.
  • Compare running kernels against vendor advisories and the CVE affected version data.
  • Confirm the installed kernel includes the relevant stable commit or vendor backport.
  • After patching, reboot where required and verify the running kernel changed.
Prepared
Confidence
high
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-400: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-47238 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
2ADP providers
8Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2021-47238Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux24803f38a5c0b6c57ed800b47e695f9ce474bc3a, 24803f38a5c0b6c57ed800b47e695f9ce474bc3a, 24803f38a5c0b6c57ed800b47e695f9ce474bc3a, 24803f38a5c0b6c57ed800b47e695f9ce474bc3a, 24803f38a5c0b6c57ed800b47e695f9ce474bc3a, 24803f38a5c0b6c57ed800b47e695f9ce474bc3a, 24803f38a5c0b6c57ed800b47e695f9ce474bc3a, bd1b664a19403ede448d29c87b2f23796bc7a577, b38c6e0bd5b5e439ecebdc0df599d573c2f610f8unaffected
LinuxLinux4.9, 0, 4.9.274, 4.14.238, 4.19.196, 5.4.128, 5.10.46, 5.12.13, 5.13affected
Weakness

CWE details

CWE-400

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-400 · source CWE mapping

Uncontrolled Resource Consumption

Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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