Security readout for executives and security teams
Plain-English summary
A Linux IPv6 networking flaw can prevent SNATed Kubernetes traffic from being recognized by transparent sockets. In the described Cilium and Envoy design, affected traffic may avoid the intended redirection into layer-seven policy enforcement. The supplied record rates it critical, but its narrative does not establish general remote kernel compromise.
Executive priority
Prioritize prompt assessment and patching where IPv6 Kubernetes traffic relies on Cilium and Envoy transparent-socket redirection. Potential failure of an enforcement control is business-significant. Avoid assuming every Linux host faces critical exposure; configuration and vendor backport status materially determine risk.
Technical view
The IPv6 nf_sk_lookup_slow_v6 path omitted the conntrack lookup used by IPv4 to recover a packet’s original tuple after SNAT. Consequently, xt_socket --transparent may not match and redirect affected IPv6 traffic. Linux stable commits add the missing lookup. Exact exposure depends on kernel version, backports, IPv6 SNAT, and transparent-socket policy architecture.
Likely exposure
Most relevant to Linux systems using IPv6 SNAT with transparent socket matching, particularly Kubernetes deployments combining Cilium, Envoy, and iptables-based redirection. Systems without this traffic path may be unaffected operationally. The bundle’s affected-version data is insufficient for dependable package-level conclusions, so distribution backports must be checked.
Exploitation context
The bundle reports that this CVE is not in KEV and provides no evidence of active exploitation or a public exploit. The described consequence is a network-policy enforcement failure under a specific IPv6 SNAT configuration, not demonstrated arbitrary code execution. Treat possible policy bypass as the principal risk supported by the sources.
Researcher notes
The supplied CVSS 10 vector asserts complete confidentiality, integrity, and availability impact, while the technical narrative specifically documents failed socket matching and redirection. It does not substantiate memory corruption, privilege escalation, or remote code execution. Researchers should distinguish the confirmed policy-path failure from broader impacts and independently map stable commits to distribution kernels.
Mitigation direction
- Install a vendor-supported kernel containing the applicable Linux stable fix or backport.
- Check Linux distribution and Kubernetes platform advisories for package-specific fixed versions.
- Prioritize clusters using IPv6 SNAT, Cilium, Envoy, and transparent socket redirection.
- If patching is delayed, obtain supported compensating controls from Linux and Cilium vendors.
Validation and detection
- Inventory kernel and distribution package versions across Kubernetes nodes and network gateways.
- Identify environments using IPv6 SNAT with xt_socket transparent matching.
- Confirm whether Cilium redirects IPv6 pod egress through Envoy for layer-seven enforcement.
- Verify installed packages include an applicable referenced stable commit or vendor backport.
- After remediation, conduct authorized tests confirming SNATed IPv6 traffic reaches intended policy enforcement.
Public sources used
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
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Container behavior lookup
The affected technology mentions containers, so container-specific ATT&CK technique review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2025-22021 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
- Critical
- CVSS
- 10 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
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.
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H3.96LinuxVulnerability scoring details
Base CVSS 3.1 score
10CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
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/6488b96a79a26e19100ad872622f04e93b638d7fCVE reference, Linux
- https://git.kernel.org/stable/c/58ab63d3ded2ca6141357a2b24eee8453d0f871dCVE reference, Linux
- https://git.kernel.org/stable/c/1ca2169cc19dca893c7aae6af122852097435d16CVE reference, Linux
- https://git.kernel.org/stable/c/1ec43100f7123010730b7ddfc3d5c2eac19e70e7CVE reference, Linux
- https://git.kernel.org/stable/c/5251041573850e5020cd447374e23010be698898CVE reference, Linux
- https://git.kernel.org/stable/c/2bb139e483f8cbe488d19d8c1135ac3615e2668cCVE reference, Linux
- https://git.kernel.org/stable/c/41904cbb343d115931d6bf79aa2c815cac4ef72bCVE reference, Linux
- https://git.kernel.org/stable/c/221c27259324ec1404f028d4f5a0f2ae7f63ee23CVE reference, Linux
- https://git.kernel.org/stable/c/932b32ffd7604fb00b5c57e239a3cc4d901ccf6eCVE reference, Linux
- https://lists.debian.org/debian-lts-announce/2025/05/msg00045.htmlCVE reference, CVE
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.htmlCVE reference, CVE
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.