boxscore/security
CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-47036MEDIUM
Linux Linux — udp: skip L4 aggregation for UDP tunnel packets
  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   L   L   L   N  U  N  N  H    5.5   .0053   42.6     —
AFFECTED
  Product  Versions                                    Fixed
  Linux    9fd1ff5d2ac7181844735806b0a703c942365291 –  —
  Linux    5.6 –                                       5.12.4
TIMELINE
  Feb 27  Reserved by Linux
  Feb 28  Published (CNA: Linux)
  Aug 4   RESCORED — CVE-2021-47036 (Linux). CVSS 9.8 → 5.5 (NVD).
CNA: Linux · CVSS v3.1 · 2 references · NVD status: Modified

Description

In the Linux kernel, the following vulnerability has been resolved: udp: skip L4 aggregation for UDP tunnel packets If NETIF_F_GRO_FRAGLIST or NETIF_F_GRO_UDP_FWD are enabled, and there are UDP tunnels available in the system, udp_gro_receive() could end-up doing L4 aggregation (either SKB_GSO_UDP_L4 or SKB_GSO_FRAGLIST) at the outer UDP tunnel level for packets effectively carrying and UDP tunnel header. That could cause inner protocol corruption. If e.g. the relevant packets carry a vxlan header, different vxlan ids will be ignored/ aggregated to the same GSO packet. Inner headers will be ignored, too, so that e.g. TCP over vxlan push packets will be held in the GRO engine till the next flush, etc. Just skip the SKB_GSO_UDP_L4 and SKB_GSO_FRAGLIST code path if the current packet could land in a UDP tunnel, and let udp_gro_receive() do GRO via udp_sk(sk)->gro_receive. The check implemented in this patch is broader than what is strictly needed, as the existing UDP tunnel could be e.g. configured on top of a different device: we could end-up skipping GRO at-all for some packets. Anyhow, that is a very thin corner case and covering it will add quite a bit of complexity. v1 -> v2: - hopefully clarify the commit message

Lifecycle

Complete event history — 3 events, chronological
DateEventDetail
February 27, 2024ReservedReserved by Linux
February 28, 2024PublishedPublished (CNA: Linux)
August 4, 2026RESCOREDRESCORED — CVE-2021-47036 (Linux). CVSS 9.8 → 5.5 (NVD).

Affected

Affected products and packages — 2 rows
VendorProduct / PackageEcosystemVersion introducedFixed
LinuxLinux9fd1ff5d2ac7181844735806b0a703c942365291
LinuxLinux5.65.12.4

References (2)

Related

Authoritative record: CVE-2021-47036 at cve.org

Vendors: linux

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-47036 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.