Date: Tue, 15 Dec 2020 12:20:24 +0000 From: Xen.org security team <security@....org> To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org, xen-users@...ts.xen.org, oss-security@...ts.openwall.com CC: Xen.org security team <security-team-members@....org> Subject: Xen Security Advisory 352 v3 (CVE-2020-29486) - oxenstored: node ownership can be changed by unprivileged clients -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2020-29486 / XSA-352 version 3 oxenstored: node ownership can be changed by unprivileged clients UPDATES IN VERSION 3 ==================== Public release. ISSUE DESCRIPTION ================= Nodes in xenstore have an ownership. In oxenstored, a owner could give a node away. But node ownership has quota implications. Any guest can run another guest out of quota, or create an unbounded number of nodes owned by dom0, thus running xenstored out of memory IMPACT ====== A malicious guest administrator can cause denial of service, against a specific guest or against the whole host. VULNERABLE SYSTEMS ================== All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable. MITIGATION ========== There are no mitigations. Changing to use of C xenstored would avoid this vulnerability. However, given the other vulnerabilities in both versions of xenstored being reported at this time, changing xenstored implementation is not a recommended approach to mitigation of individual issues. CREDITS ======= This issue was discovered by Edwin Török of Citrix. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. Note that patches for released versions are generally prepared to apply to the stable branches, and may not apply cleanly to the most recent release tarball. Downstreams are encouraged to update to the tip of the stable branch before applying these patches. xsa352.patch xen-unstable - 4.10 $ sha256sum xsa352* a3b2b2bd4c6b49c472df23f88fb9a5e204d2ba3cd0c3901f8ed057566ef98c85 xsa352.meta 6f9798e20282d4e06f0a8a1abd0d147649e20b33c21559d5a1ea0b1a73a2a4e4 xsa352.patch $ DEPLOYMENT DURING EMBARGO ========================= Deployment of the patches and/or mitigations described above (or others which are substantially similar) is permitted during the embargo, even on public-facing systems with untrusted guest users and administrators. But: Distribution of updated software is prohibited (except to other members of the predisclosure list). Predisclosure list members who wish to deploy significantly different patches and/or mitigations, please contact the Xen Project Security Team. (Note: this during-embargo deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable. This is to enable the community to have oversight of the Xen Project Security Team's decisionmaking.) For more information about permissible uses of embargoed information, consult the Xen Project community's agreed Security Policy: http://www.xenproject.org/security-policy.html -----BEGIN PGP SIGNATURE----- iQFABAEBCAAqFiEEI+MiLBRfRHX6gGCng/4UyVfoK9kFAl/Yqd8MHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZ/JgH/Rb3BDBjWi+fTDsPMr21yDsrCWGzpyBabflpglQt b3rTDEx7YlNCkb32xYvZLR9mGAGg8X01zIQVKOQ10Hnib6Vx4TvcdwPqSYGMn3U6 4g3TmWpZJZNfCIbdznXGhOmTLZzVEGDZu1+S+mE3aAdtDGEE98p9P/J43dEt/kWX R/DcMrCe9LOHKi+MCxZqAFlbZ79QJls6G/sH6VWSUp/Bq8hCtsd/C0Jk3LIBZgnW V3SUYLhR7Tp7Pkda4m4lVLlvCo+9jlVwevs/MmvyFulxUrDN1/9LrHpZyJ7ZMBwt 2N7zpJpdrY5JiEH6d4fuVUsH78+9+zVxs5PFDXUc7ud2QyA= =ofMB -----END PGP SIGNATURE----- Download attachment "xsa352.meta" of type "application/octet-stream" (2316 bytes) Download attachment "xsa352.patch" of type "application/octet-stream" (1838 bytes)
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