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CVE Record

CVE-2021-47080: RDMA/core: Prevent divide-by-zero error triggered by the user

In the Linux kernel, the following vulnerability has been resolved: RDMA/core: Prevent divide-by-zero error triggered by the user The user_entry_size is supplied by the user and later used as a denominator to calculate number of entries. The zero supplied by the user will trigger the following divide-by-zero error: divide error: 0000 [#1] SMP KASAN PTI CPU: 4 PID: 497 Comm: c_repro Not tainted 5.13.0-rc1+ #281 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:ib_uverbs_handler_UVERBS_METHOD_QUERY_GID_TABLE+0x1b1/0x510 Code: 87 59 03 00 00 e8 9f ab 1e ff 48 8d bd a8 00 00 00 e8 d3 70 41 ff 44 0f b7 b5 a8 00 00 00 e8 86 ab 1e ff 31 d2 4c 89 f0 31 ff <49> f7 f5 48 89 d6 48 89 54 24 10 48 89 04 24 e8 1b ad 1e ff 48 8b RSP: 0018:ffff88810416f828 EFLAGS: 00010246 RAX: 0000000000000008 RBX: 1ffff1102082df09 RCX: ffffffff82183f3d RDX: 0000000000000000 RSI: ffff888105f2da00 RDI: 0000000000000000 RBP: ffff88810416fa98 R08: 0000000000000001 R09: ffffed102082df5f R10: ffff88810416faf7 R11: ffffed102082df5e R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000008 R15: ffff88810416faf0 FS: 00007f5715efa740(0000) GS:ffff88811a700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000840 CR3: 000000010c2e0001 CR4: 0000000000370ea0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? ib_uverbs_handler_UVERBS_METHOD_INFO_HANDLES+0x4b0/0x4b0 ib_uverbs_cmd_verbs+0x1546/0x1940 ib_uverbs_ioctl+0x186/0x240 __x64_sys_ioctl+0x38a/0x1220 do_syscall_64+0x3f/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-47080 is a Linux kernel RDMA flaw where user-supplied input can trigger a divide-by-zero crash path. The public record describes a kernel fault, not data theft or privilege escalation. Business impact is mainly availability risk on affected Linux systems where the RDMA user verbs path is reachable.

Executive priority

Patch during normal vulnerability maintenance, faster for shared compute, HPC, or RDMA-enabled infrastructure. No source supports emergency treatment for internet-scale exploitation, but kernel crashes can disrupt important workloads.

Technical view

The issue is in Linux RDMA/core. A user-controlled user_entry_size value is later used as a denominator in the QUERY_GID_TABLE uverbs handler, allowing zero to trigger a kernel divide error through an ioctl path. Sources list stable kernel commits as the resolution, but provide no CVSS score or CWE.

Likely exposure

Exposure is likely limited to Linux systems running affected kernel versions and using or exposing RDMA/uverbs functionality. The source bundle lists Linux 5.10, 5.12.7, and 5.13-related affected version data, but distro backports must be verified separately.

Exploitation context

The bundle shows a user-triggered kernel crash trace and says the value is supplied by the user. It does not cite active exploitation, public exploit use, remote reachability, or KEV listing. Treat this as a local availability concern unless vendor advisories say otherwise.

Researcher notes

Evidence supports a user-controlled divide-by-zero in ib_uverbs_handler_UVERBS_METHOD_QUERY_GID_TABLE. The record lacks CVSS, CWE, distro package status, and exploit maturity details. Avoid assuming privilege escalation or remote attack paths without additional vendor evidence.

Mitigation direction

  • Upgrade to a kernel build containing the referenced stable fixes.
  • Confirm whether your Linux distribution backported the fix.
  • Prioritize hosts using RDMA, InfiniBand, or uverbs functionality.
  • Check vendor guidance before relying on access restrictions as mitigation.
  • Track this under availability risk until patched.

Validation and detection

  • Inventory kernel versions across Linux hosts.
  • Identify systems with RDMA or uverbs functionality enabled.
  • Map installed kernels against vendor fixed package versions.
  • Verify patch status against the three referenced stable commits.
  • Review crash logs for divide errors in RDMA uverbs handlers.
Prepared
Confidence
medium
Sources
5

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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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
4Source 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

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux9f85cbe50aa044a46f0a22fda323fa27b80c82da, 9f85cbe50aa044a46f0a22fda323fa27b80c82da, 9f85cbe50aa044a46f0a22fda323fa27b80c82daunaffected
LinuxLinux5.10, 0, 5.10.40, 5.12.7, 5.13affected
Weakness

CWE details

No CWE listed

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