Headline
CVE-2023-34319: 432 - Xen Security Advisories
The fix for XSA-423 added logic to Linux’es netback driver to deal with a frontend splitting a packet in a way such that not all of the headers would come in one piece. Unfortunately the logic introduced there didn’t account for the extreme case of the entire packet being split into as many pieces as permitted by the protocol, yet still being smaller than the area that’s specially dealt with to keep all (possible) headers together. Such an unusual packet would therefore trigger a buffer overrun in the driver.
Information
Advisory
XSA-432
Public release
2023-08-08 15:53
Updated
2023-08-08 15:53
Version
2
CVE(s)
CVE-2023-34319
Title
Linux: buffer overrun in netback due to unusual packet
Filesadvisory-432.txt (signed advisory file)
xsa432-linux.patchAdvisory
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256
Xen Security Advisory CVE-2023-34319 / XSA-432
version 2
Linux: buffer overrun in netback due to unusual packet
UPDATES IN VERSION 2
Public release.
ISSUE DESCRIPTION
The fix for XSA-423 added logic to Linux’es netback driver to deal with a frontend splitting a packet in a way such that not all of the headers would come in one piece. Unfortunately the logic introduced there didn’t account for the extreme case of the entire packet being split into as many pieces as permitted by the protocol, yet still being smaller than the area that’s specially dealt with to keep all (possible) headers together. Such an unusual packet would therefore trigger a buffer overrun in the driver.
IMPACT
An unprivileged guest can cause Denial of Service (DoS) of the host by sending network packets to the backend, causing the backend to crash.
Data corruption or privilege escalation seem unlikely but have not been ruled out.
VULNERABLE SYSTEMS
All systems using a Linux based network backend with kernel 3.19 and newer are vulnerable, on the assumption that the fix for XSA-423 was taken. Systems using other network backends are not known to be vulnerable.
MITIGATION
Using another PV network backend (e.g. the qemu based “qnic” backend) will mitigate the problem.
Using a dedicated network driver domain per guest will mitigate the problem.
CREDITS
This issue was discovered by Ross Lagerwall of Citrix.
RESOLUTION
Applying the attached patch resolves this issue.
xsa432-linux.patch Linux 6.3 - 6.5-rc
$ sha256sum xsa432* bf7acd23be1d185c40aca8b4f7700e25afd482d9ac8671ae22b021380b059091 xsa432-linux.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-----
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Xenproject.org Security Team
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