Security readout for executives and security teams
Plain-English summary
CVE-2021-47606 is a Linux kernel flaw where an empty netlink packet can trigger a divide-by-zero crash in the netem queuing path. The business impact is availability risk, not proven data theft. The supplied sources do not provide CVSS, confirmed exploitation, or distribution-specific advisories.
Executive priority
Schedule remediation in the normal kernel patch cycle, escalating for shared infrastructure where a crash could affect multiple tenants or services. There is no supplied evidence of active exploitation or data compromise, but kernel availability bugs deserve disciplined tracking.
Technical view
The fix adds a length check in af_netlink to prevent empty sk_buffs. Without it, skb->len and data_len can both be zero, and netem_enqueue may divide by zero during randomized corruption handling. The crash trace shows netlink_sendmsg reaching netem_enqueue in a Linux 5.16-rc1 test environment.
Likely exposure
Exposure is most relevant to Linux systems running affected kernel versions or missing the referenced stable commits. The bundle lists Linux as affected and references fixes across stable branches, but it does not identify specific distributions, configurations, or remote reachability.
Exploitation context
The source bundle includes a reproducer crash trace and states the vulnerability was resolved in Linux. It does not cite active exploitation, public weaponization, or CISA KEV listing. Treat exploitation as unconfirmed based on the provided evidence.
Researcher notes
Key uncertainty is impact boundary. The trace shows local netlink sendmsg leading to netem_enqueue, but the bundle does not define required privileges, namespace conditions, or distro backports. Avoid assuming remote exploitability without additional vendor or kernel analysis.
Mitigation direction
- Update Linux kernels through normal vendor or distribution channels.
- Confirm the installed kernel includes the relevant upstream stable fix.
- Prioritize shared, multi-user, or externally exposed Linux hosts.
- Check vendor guidance if a fixed package is unavailable.
- Track kernel update status in vulnerability management records.
Validation and detection
- Inventory Linux kernel versions across servers and appliances.
- Compare running kernels against vendor advisories or referenced stable commits.
- Review whether affected systems use netem or related traffic-control functionality.
- Confirm patched systems are rebooted into the fixed kernel.
- Document exceptions where vendor status remains unclear.
Public sources used
- CVE Program
- CVE List V5
- Linux stable commit c54a60c8fbaa774f828e26df79f66229a8a0e010
- Linux stable commit 40cf2e058832d9cfaae98dfd77334926275598b6
- Linux stable commit 54e785f7d5c197bc06dbb8053700df7e2a093ced
- Linux stable commit ff3f517bf7138e01a17369042908a3f345c0ee41
- Linux stable commit c0315e93552e0d840e9edc6abd71c7db82ec8f51
- Linux stable commit dadce61247c6230489527cc5e343b6002d1114c5
- Linux stable commit 4c986072a8c9249b9398c7a18f216dc26a9f0e35
- Linux stable commit f123cffdd8fe8ea6c7fded4b88516a42798797d0
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2021-47606 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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.
SSVC decision data
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/c54a60c8fbaa774f828e26df79f66229a8a0e010CVE reference, Linux
- https://git.kernel.org/stable/c/40cf2e058832d9cfaae98dfd77334926275598b6CVE reference, Linux
- https://git.kernel.org/stable/c/54e785f7d5c197bc06dbb8053700df7e2a093cedCVE reference, Linux
- https://git.kernel.org/stable/c/ff3f517bf7138e01a17369042908a3f345c0ee41CVE reference, Linux
- https://git.kernel.org/stable/c/c0315e93552e0d840e9edc6abd71c7db82ec8f51CVE reference, Linux
- https://git.kernel.org/stable/c/dadce61247c6230489527cc5e343b6002d1114c5CVE reference, Linux
- https://git.kernel.org/stable/c/4c986072a8c9249b9398c7a18f216dc26a9f0e35CVE reference, Linux
- https://git.kernel.org/stable/c/f123cffdd8fe8ea6c7fded4b88516a42798797d0CVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.