CVE-2020-11091Weave Net clusters susceptible to MitM attacks via IPv6 rogue router advertisements
- 5.8MediumCVSS base score
- 0.86%Exploitation in 30 daysEPSS · top 41% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In Weave Net before version 2.6.3, an attacker able to run a process as root in a container is able to respond to DNS requests from the host and thereby insert themselves as a fake service. In a cluster with an IPv4 internal network, if IPv6 is not totally disabled on the host (via ipv6.disable=1 on the kernel cmdline), it will be either unconfigured or configured on some interfaces, but it's pretty likely that ipv6 forwarding is disabled, ie /proc/sys/net/ipv6/conf//forwarding == 0. Also by default, /proc/sys/net/ipv6/conf//accept_ra == 1. The combination of these 2 sysctls means that the host accepts router advertisements and configure the IPv6 stack using them. By sending rogue router advertisements, an attacker can reconfigure the host to redirect part or all of the IPv6 traffic of the host to the attacker controlled container. Even if there was no IPv6 traffic before, if the DNS returns A (IPv4) and AAAA (IPv6) records, many HTTP libraries will try to connect via IPv6 first then fallback to IPv4, giving an opportunity to the attacker to respond. If by chance you also have on the host a vulnerability like last year's RCE in apt (CVE-2019-3462), you can now escalate to the host. Weave Net version 2.6.3 disables the accept_ra option on the veth devices that it creates.
Timeline
ID reserved
By GitHub_M
- 2 months later
· 2 months later
Published
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:H/A:N |
| NVDNVD · Modified | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.86% · top 41% of all CVEs (12 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.8.
Affected products
- affected < 2.6.3
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/weaveworks/weaveGHSA-59qg-grp7-5r73 (opens in a new tab)
References
References2
- https://github.com/weaveworks/weave/security/advisories/GHSA-59qg-grp7-5r73 (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/weaveworks/weave/commit/15f21f1899060f7716c70a8555a084e836f39a60 (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-0955 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-59qg-grp7-5r73 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2020-11091)Record last updated .