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OSEC-2022-01
No affected components available
Background
MirageOS is a library operating system using cooperative multitasking, which can be executed as a guest of the Xen hypervisor. Output on the console is performed via the Xen console protocol. Problem Description
Since MirageOS moved from PV mode to PVH, and thus replacing Mini-OS with solo5, there was an issue in the solo5 code which failed to properly account the already written bytes on the console. This only occurs if the output to be performed does not fit in a single output buffer (2048 bytes on Xen).
The code in question set the number of bytes written to the last written count (written = output_some(buf)), instead of increasing the written count (written += output_some(buf)).
Impact
Console output may lead to an infinite loop, endlessly printing data onto the console.
A prominent unikernel is the Qubes MirageOS firewall, which prints some input packets onto the console. This can lead to a remote denial of service vulnerability, since any client could send a malformed and sufficiently big network packet.
Solution
The solution is to fix the console output code in solo5, as done in https://github.com/Solo5/solo5/pull/538/commits/099be86f0a17a619fcadbb970bb9e511d28d3cd8
Timeline
- 2022-12-04: initial report by Krzysztof Burghardt https://github.com/mirage/qubes-mirage-firewall/issues/166
- 2022-12-04: investigation by Hannes Mehnert and Pierre Alain
- 2022-12-05: initial fix by Pierre Alain https://github.com/Solo5/solo5/pull/538
- 2022-12-05: review of fix by Thomas Leonard
- 2022-12-07: release of fixed packages and security advisory
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is moderate. The vulnerability is likely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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