Bug 1848000 (CVE-2020-11017)
| Summary: | CVE-2020-11017 freerdp: Double free in cliprdr_server_receive_capabilities could result in data corruption | ||
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| Product: | [Other] Security Response | Reporter: | Michael Kaplan <mkaplan> |
| Component: | vulnerability | Assignee: | Red Hat Product Security <security-response-team> |
| Status: | CLOSED NOTABUG | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | unspecified | CC: | mads, mailinglists, negativo17, oholy, pahan |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | freerdp 2.1.0 | Doc Type: | If docs needed, set a value |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2020-06-23 05:20:26 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | 1848001, 1848002, 1848003 | ||
| Bug Blocks: | 1848044 | ||
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Description
Michael Kaplan
2020-06-17 14:16:51 UTC
Created freerdp tracking bugs for this issue: Affects: epel-all [bug 1848001] Affects: fedora-all [bug 1848002] Created freerdp1.2 tracking bugs for this issue: Affects: fedora-all [bug 1848003] Technical Summary: The freerdp server function cliprdr_server_receive_capabilities() reads data bytes out of an input stream that is received from the freerdp client application. One data point that is read by cliprdr_server_receive_capabilities() is the UINT16, capabilitySetLength. capabilitySetLength is used to control the caps_set_size variable, that is subsequently passed in a call to realloc()[1] as the size parameter. A malicious client could cause a call to realloc(capabilities.capabilitySets, 0), which would free the memory pointed to by capabilities.capabilitySets[2]. The code directly after the call to realloc() checks for NULL in order to avoid a potential NULL pointer reference in the case where realloc() were to fail. However, the code attempts to free capabilities.capabilitySets if the return from realloc() is NULL. This is a problem because a call to realloc(capabilities.capabilitySets, 0) will have already freed the memory pointed to by capabilities.capabilitySets and thus trigger a double-free if capabilitySetLength is 0. Exploiting this flaw could crash the freerdp server remotely and lead to a denial of service. The vulnerable functionality is in the clipboard functionality, which can be disabled in the server settings. 1. https://github.com/FreeRDP/FreeRDP/blob/aa07efeb18ac9eb8df3ce8410b116b8c4b080270/channels/cliprdr/server/cliprdr_main.c#L489 2. https://linux.die.net/man/3/realloc Statement: This flaw does not affect any versions of freerdp as shipped with Red Hat Enterprise Linux. Versions of freerdp shipped with Red Hat Enterprise Linux 6, 7, and 8 do not have the vulnerable code. Mitigation: Disable clipboard functionality in the freerdp server settings. This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2020-11017 |