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CVE Record

CVE-2021-47146: mld: fix panic in mld_newpack()

In the Linux kernel, the following vulnerability has been resolved: mld: fix panic in mld_newpack() mld_newpack() doesn't allow to allocate high order page, only order-0 allocation is allowed. If headroom size is too large, a kernel panic could occur in skb_put(). Test commands: ip netns del A ip netns del B ip netns add A ip netns add B ip link add veth0 type veth peer name veth1 ip link set veth0 netns A ip link set veth1 netns B ip netns exec A ip link set lo up ip netns exec A ip link set veth0 up ip netns exec A ip -6 a a 2001:db8:0::1/64 dev veth0 ip netns exec B ip link set lo up ip netns exec B ip link set veth1 up ip netns exec B ip -6 a a 2001:db8:0::2/64 dev veth1 for i in {1..99} do let A=$i-1 ip netns exec A ip link add ip6gre$i type ip6gre \ local 2001:db8:$A::1 remote 2001:db8:$A::2 encaplimit 100 ip netns exec A ip -6 a a 2001:db8:$i::1/64 dev ip6gre$i ip netns exec A ip link set ip6gre$i up ip netns exec B ip link add ip6gre$i type ip6gre \ local 2001:db8:$A::2 remote 2001:db8:$A::1 encaplimit 100 ip netns exec B ip -6 a a 2001:db8:$i::2/64 dev ip6gre$i ip netns exec B ip link set ip6gre$i up done Splat looks like: kernel BUG at net/core/skbuff.c:110! invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI CPU: 0 PID: 7 Comm: kworker/0:1 Not tainted 5.12.0+ #891 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:skb_panic+0x15d/0x15f Code: 92 fe 4c 8b 4c 24 10 53 8b 4d 70 45 89 e0 48 c7 c7 00 ae 79 83 41 57 41 56 41 55 48 8b 54 24 a6 26 f9 ff <0f> 0b 48 8b 6c 24 20 89 34 24 e8 4a 4e 92 fe 8b 34 24 48 c7 c1 20 RSP: 0018:ffff88810091f820 EFLAGS: 00010282 RAX: 0000000000000089 RBX: ffff8881086e9000 RCX: 0000000000000000 RDX: 0000000000000089 RSI: 0000000000000008 RDI: ffffed1020123efb RBP: ffff888005f6eac0 R08: ffffed1022fc0031 R09: ffffed1022fc0031 R10: ffff888117e00187 R11: ffffed1022fc0030 R12: 0000000000000028 R13: ffff888008284eb0 R14: 0000000000000ed8 R15: 0000000000000ec0 FS: 0000000000000000(0000) GS:ffff888117c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8b801c5640 CR3: 0000000033c2c006 CR4: 00000000003706f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? ip6_mc_hdr.isra.26.constprop.46+0x12a/0x600 ? ip6_mc_hdr.isra.26.constprop.46+0x12a/0x600 skb_put.cold.104+0x22/0x22 ip6_mc_hdr.isra.26.constprop.46+0x12a/0x600 ? rcu_read_lock_sched_held+0x91/0xc0 mld_newpack+0x398/0x8f0 ? ip6_mc_hdr.isra.26.constprop.46+0x600/0x600 ? lock_contended+0xc40/0xc40 add_grhead.isra.33+0x280/0x380 add_grec+0x5ca/0xff0 ? mld_sendpack+0xf40/0xf40 ? lock_downgrade+0x690/0x690 mld_send_initial_cr.part.34+0xb9/0x180 ipv6_mc_dad_complete+0x15d/0x1b0 addrconf_dad_completed+0x8d2/0xbb0 ? lock_downgrade+0x690/0x690 ? addrconf_rs_timer+0x660/0x660 ? addrconf_dad_work+0x73c/0x10e0 addrconf_dad_work+0x73c/0x10e0 Allowing high order page allocation could fix this problem.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-47146 is a Linux kernel flaw in IPv6 multicast listener handling that can trigger a kernel panic. The public record describes a crash, not data theft or privilege escalation. Business impact is primarily availability: affected hosts could reboot or stop service if the vulnerable path is reached.

Executive priority

Treat this as a moderate availability risk. Patch during normal kernel maintenance unless affected systems are critical, multi-tenant, or exposed to users with network administration privileges. There is no cited evidence of active exploitation.

Technical view

The issue is in mld_newpack(). The source says only order-0 allocation was allowed; excessive headroom could cause skb_put() to panic. The stack trace involves IPv6 multicast, address configuration, and MLD packet construction. Linux stable fix commits are referenced across maintained kernel branches.

Likely exposure

Exposure is most relevant to Linux systems using affected kernel versions with IPv6 networking paths enabled. The provided reproduction context uses network namespace and IPv6 tunnel configuration, suggesting privileged network configuration is involved, but the source does not define attacker prerequisites or remote reachability.

Exploitation context

No active exploitation is indicated: KEV is false, and the bundle provides no exploitation reports. The source includes a technical crash reproduction, but no evidence of weaponized exploitation or remote unauthenticated attack capability.

Researcher notes

The evidence supports a kernel panic in the IPv6 MLD packet path, fixed by Linux stable commits. CVSS, CWE, and attacker requirements are absent from the provided bundle, so exploitability beyond denial of service should not be assumed.

Mitigation direction

  • Update to a kernel containing the referenced stable fix commits.
  • Check Linux distribution advisories for backported CVE-2021-47146 fixes.
  • Prioritize internet-facing or multi-tenant Linux systems using IPv6 networking.
  • Limit untrusted access to privileged network administration capabilities until patched.
  • Review crash monitoring for kernel panics involving MLD or skb_put().

Validation and detection

  • Inventory Linux kernel versions across servers, containers hosts, and appliances.
  • Confirm vendor packages include a CVE-2021-47146 backport or equivalent stable commit.
  • Review kernel logs for skb_panic, mld_newpack, or IPv6 addrconf crash traces.
  • Verify IPv6 networking and tunnel features are not unnecessarily enabled.
  • Record exception owners for systems awaiting vendor kernel updates.
Prepared
Confidence
medium
Sources
10

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2021-47146 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
2ADP providers
9Source links

SSVC decision data

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

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

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux72e09ad107e78d69ff4d3b97a69f0aad2b77280f, 72e09ad107e78d69ff4d3b97a69f0aad2b77280f, 72e09ad107e78d69ff4d3b97a69f0aad2b77280f, 72e09ad107e78d69ff4d3b97a69f0aad2b77280f, 72e09ad107e78d69ff4d3b97a69f0aad2b77280f, 72e09ad107e78d69ff4d3b97a69f0aad2b77280f, 72e09ad107e78d69ff4d3b97a69f0aad2b77280f, 72e09ad107e78d69ff4d3b97a69f0aad2b77280funaffected
LinuxLinux2.6.35, 0, 4.4.271, 4.9.271, 4.14.235, 4.19.193, 5.4.124, 5.10.42, 5.12.9, 5.13affected
Weakness

CWE details

No CWE listed

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