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CVE-2026-32241

Flannel vulnerable to cross-node remote code execution via extension backend BackendData injection

7.5 HighFix available

Flannel is a network fabric for containers, designed for Kubernetes. The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. In versions of Flannel prior to 0.28.2, this Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster. The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks. Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. The vulnerability is fixed in version v0.28.2. As a workaround, use Flannel with another backend such as vxlan or wireguard.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

2.76%Up 2.6 points since Mar 28, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.5

Flannel vulnerable to cross-node remote code execution via extension backend BackendData injection

Flannel is a network fabric for containers, designed for Kubernetes. The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. In versions of Flannel prior to 0.28.2, this Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster. The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks. Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. The vulnerability is fixed in version v0.28.2. As a workaround, use Flannel with another backend such as vxlan or wireguard.

Record
CVE-2026-32241
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-77
Updated
2026-11-02
EUVDEUVD-2026-16771 7.5

Flannel is a network fabric for containers, designed for Kubernetes. The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. In versions of Flannel prior to 0.28.2, this Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster. The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks. Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. The vulnerability is fixed in version v0.28.2. As a workaround, use Flannel with another backend such as vxlan or wireguard.

Record
EUVD-2026-16771
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-vchx-5pr6-ffx2 7.5

Flannel has cross-node remote code execution via extension backend BackendData injection

Background

The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. This backend uses shell commands stored in Kubernetes annotations to configure network connectivity on the node.

Note: consumers are only affected by this vulnerability if they use the experimental Extension backend. Other backends such as vxlan and wireguard are unaffected.

Vulnerability

This Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster.

The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks.

Impact

Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected.

Patches

This is fixed in version v0.28.2.

Workaround

If consumers cannot update to a patched version, then use Flannel with another backend such as vxlan or wireguard.

Credits

Flannel would like to thank Shachar Tal from Palo Alto Networks for reporting this vulnerability.

Record
GHSA-vchx-5pr6-ffx2
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-77, CWE-78
Updated
2026-11-02
NVD 7.5

Flannel is a network fabric for containers, designed for Kubernetes. The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. In versions of Flannel prior to 0.28.2, this Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster. The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks. Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. The vulnerability is fixed in version v0.28.2. As a workaround, use Flannel with another backend such as vxlan or wireguard.

Record
CVE-2026-32241
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-77
Updated
2026-11-02
OSV 7.5

Flannel vulnerable to cross-node remote code execution via extension backend BackendData injection

Flannel is a network fabric for containers, designed for Kubernetes. The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. In versions of Flannel prior to 0.28.2, this Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster. The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks. Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. The vulnerability is fixed in version v0.28.2. As a workaround, use Flannel with another backend such as vxlan or wireguard.

Record
CVE-2026-32241
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-77
Updated
2026-11-02
OSVGHSA-vchx-5pr6-ffx2 7.5

Flannel has cross-node remote code execution via extension backend BackendData injection

Background

The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. This backend uses shell commands stored in Kubernetes annotations to configure network connectivity on the node.

Note: consumers are only affected by this vulnerability if they use the experimental Extension backend. Other backends such as vxlan and wireguard are unaffected.

Vulnerability

This Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster.

The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks.

Impact

Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected.

Patches

This is fixed in version v0.28.2.

Workaround

If consumers cannot update to a patched version, then use Flannel with another backend such as vxlan or wireguard.

Credits

Flannel would like to thank Shachar Tal from Palo Alto Networks for reporting this vulnerability.

Record
GHSA-vchx-5pr6-ffx2
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-77, CWE-78
Updated
2026-11-02
Show 5 moreShow less
OSVAZL-80972 No score

CVE-2026-32241 affecting package flannel for versions less than 0.24.2-26

Flannel is a network fabric for containers, designed for Kubernetes. The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. In versions of Flannel prior to 0.28.2, this Extension backend is vulnerable to a command injection that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster. The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the flannel.alpha.coreos.com/backend-data Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks. Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. The vulnerability is fixed in version v0.28.2. As a workaround, use Flannel with another backend such as vxlan or wireguard.

Record
AZL-80972
Updated
2026-11-05
OSVGO-2026-4894 No score

Flannel has cross-node remote code execution via extension backend BackendData injection in github.com/flannel-io/flannel

Flannel has cross-node remote code execution via extension backend BackendData injection in github.com/flannel-io/flannel

Record
GO-2026-4894
Updated
2026-11-02
OSVopenSUSE-SU-2026:12270-1 No score

flannel-0.28.10-1.1 on GA media

These are all security issues fixed in the flannel-0.28.10-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:12270-1
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02
OSVSUSE-SU-2026:1205-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

Update to version 0.0.20260402T184258 2026-04-02T18:42:58Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4518 CVE-2026-32286 GHSA-jqcq-xjh3-6g23
  • GO-2026-4753 CVE-2026-33487 GHSA-479m-364c-43vc
  • GO-2026-4760 GHSA-hwqm-qvj9-4jr2
  • GO-2026-4762 CVE-2026-33186 GHSA-p77j-4mvh-x3m3
  • GO-2026-4764 GHSA-pcgw-qcv5-h8ch
  • GO-2026-4858 CVE-2026-33747 GHSA-4c29-8rgm-jvjj
  • GO-2026-4859 CVE-2026-33748 GHSA-4vrq-3vrq-g6gg
  • GO-2026-4863 GHSA-g9ww-x58f-9g6m
  • GO-2026-4872 CVE-2026-33907 GHSA-55q8-2gwx-29pc
  • GO-2026-4873 CVE-2026-33906 GHSA-87j9-m7x6-hvw2
  • GO-2026-4874 CVE-2026-33904 GHSA-9h59-p45g-445h
  • GO-2026-4875 CVE-2026-33903 GHSA-f2f3-9cx3-wcmf
  • GO-2026-4876 GHSA-prh4-vhfh-24mj
  • GO-2026-4880 CVE-2026-32695 GHSA-67jx-r9pv-98rj
  • GO-2026-4883 CVE-2026-33997 GHSA-pxq6-2prw-chj9
  • GO-2026-4887 CVE-2026-34040 GHSA-x744-4wpc-v9h2
  • GO-2026-4888 CVE-2026-26060 GHSA-3458-r943-hmx4
  • GO-2026-4889 CVE-2026-26061 GHSA-99hj-44vg-hfcp
  • GO-2026-4890 CVE-2026-34042 GHSA-x34h-54cw-9825
  • GO-2026-4891 CVE-2026-34041 GHSA-xmgr-9pqc-h5vw
  • GO-2026-4892 CVE-2026-29180 GHSA-m2h6-4xpq-qw3m
  • GO-2026-4893 CVE-2026-33433 GHSA-qr99-7898-vr7c
  • GO-2026-4894 CVE-2026-32241 GHSA-vchx-5pr6-ffx2
  • GO-2026-4896 CVE-2026-34204 GHSA-3rh2-v3gr-35p9
  • GO-2026-4897 GHSA-46wh-3698-f2cx
  • GO-2026-4899 GHSA-c279-989m-238f
  • GO-2026-4901 CVE-2026-33030 GHSA-5hf2-vhj6-gj9m
  • GO-2026-4902 CVE-2026-33029 GHSA-cp8r-8jvw-v3qg
  • GO-2026-4903 CVE-2026-33026 GHSA-fhh2-gg7w-gwpq
  • GO-2026-4904 CVE-2026-33032 GHSA-h6c2-x2m2-mwhf
  • GO-2026-4905 CVE-2026-27018 GHSA-jjwv-57xh-xr6r
  • GO-2026-4906 CVE-2026-33028 GHSA-m468-xcm6-fxg4
  • GO-2026-4907 CVE-2026-33027 GHSA-m8p8-53vf-8357
  • GO-2026-4911 CVE-2026-33990 GHSA-x2f5-332j-9xwq
  • GO-2026-4912 CVE-2026-34389 GHSA-4f9r-x588-pp2h
  • GO-2026-4913 CVE-2026-34386 GHSA-9p23-p2m4-2r4m
  • GO-2026-4914 CVE-2026-34385 GHSA-v895-833r-8c45
  • GO-2026-4915 CVE-2026-34388 GHSA-w254-4hp5-7cvv
  • GO-2026-4916 CVE-2026-26233 GHSA-247x-7qw8-fp98
  • GO-2026-4919 CVE-2026-33634 GHSA-69fq-xp46-6x23
Record
SUSE-SU-2026:1205-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/flannel-io/flannel
Go
 through 0.28.1
0.28.2
flannel
Azure Linux:3
 before 0.24.2-26
0.24.2-26
github.com/flannel-io/flannel
Go
 before 0.28.2
0.28.2
govulncheck-vulndb
openSUSE:Leap 15.6
From an advisory covering 34 CVEs
 before 0.0.20260402T184258-150000.1.158.1
0.0.20260402T184258-150000.1.158.1
flannel
openSUSE:Tumbleweed
From an advisory covering 4 CVEs
 before 0.28.10-1.1
0.28.10-1.1
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected
factsOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-32241 is a high vulnerability (CVSS 7.5) in Flannel-io Flannel, published March 27, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.76%, the 86th percentile. Fixed in github.com/flannel-io/flannel 0.28.2.

References

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