ID CVE-2018-12892
Summary An issue was discovered in Xen 4.7 through 4.10.x. libxl fails to pass the readonly flag to qemu when setting up a SCSI disk, due to what was probably an erroneous merge conflict resolution. Malicious guest administrators or (in some situations) users may be able to write to supposedly read-only disk images. Only emulated SCSI disks (specified as "sd" in the libxl disk configuration, or an equivalent) are affected. IDE disks ("hd") are not affected (because attempts to make them readonly are rejected). Additionally, CDROM devices (that is, devices specified to be presented to the guest as CDROMs, regardless of the nature of the backing storage on the host) are not affected; they are always read only. Only systems using qemu-xen (rather than qemu-xen-traditional) as the device model version are vulnerable. Only systems using libxl or libxl-based toolstacks are vulnerable. (This includes xl, and libvirt with the libxl driver.) The vulnerability is present in Xen versions 4.7 and later. (In earlier versions, provided that the patch for XSA-142 has been applied, attempts to create read only disks are rejected.) If the host and guest together usually support PVHVM, the issue is exploitable only if the malicious guest administrator has control of the guest kernel or guest kernel command line.
References
Vulnerable Configurations
  • Debian Linux 9.0
    cpe:2.3:o:debian:debian_linux:9.0
  • Xen 4.7.1
    cpe:2.3:o:xen:xen:4.7.1
  • Xen 4.8.0
    cpe:2.3:o:xen:xen:4.8.0
  • Xen 4.8.1
    cpe:2.3:o:xen:xen:4.8.1
  • Xen 4.9.0 Release Candidate 7
    cpe:2.3:o:xen:xen:4.9.0:rc7
CVSS
Base: 6.5
Impact:
Exploitability:
CWE CWE-200
CAPEC
  • Subverting Environment Variable Values
    The attacker directly or indirectly modifies environment variables used by or controlling the target software. The attacker's goal is to cause the target software to deviate from its expected operation in a manner that benefits the attacker.
  • Footprinting
    An attacker engages in probing and exploration activity to identify constituents and properties of the target. Footprinting is a general term to describe a variety of information gathering techniques, often used by attackers in preparation for some attack. It consists of using tools to learn as much as possible about the composition, configuration, and security mechanisms of the targeted application, system or network. Information that might be collected during a footprinting effort could include open ports, applications and their versions, network topology, and similar information. While footprinting is not intended to be damaging (although certain activities, such as network scans, can sometimes cause disruptions to vulnerable applications inadvertently) it may often pave the way for more damaging attacks.
  • Exploiting Trust in Client (aka Make the Client Invisible)
    An attack of this type exploits a programs' vulnerabilities in client/server communication channel authentication and data integrity. It leverages the implicit trust a server places in the client, or more importantly, that which the server believes is the client. An attacker executes this type of attack by placing themselves in the communication channel between client and server such that communication directly to the server is possible where the server believes it is communicating only with a valid client. There are numerous variations of this type of attack.
  • Browser Fingerprinting
    An attacker carefully crafts small snippets of Java Script to efficiently detect the type of browser the potential victim is using. Many web-based attacks need prior knowledge of the web browser including the version of browser to ensure successful exploitation of a vulnerability. Having this knowledge allows an attacker to target the victim with attacks that specifically exploit known or zero day weaknesses in the type and version of the browser used by the victim. Automating this process via Java Script as a part of the same delivery system used to exploit the browser is considered more efficient as the attacker can supply a browser fingerprinting method and integrate it with exploit code, all contained in Java Script and in response to the same web page request by the browser.
  • Session Credential Falsification through Prediction
    This attack targets predictable session ID in order to gain privileges. The attacker can predict the session ID used during a transaction to perform spoofing and session hijacking.
  • Reusing Session IDs (aka Session Replay)
    This attack targets the reuse of valid session ID to spoof the target system in order to gain privileges. The attacker tries to reuse a stolen session ID used previously during a transaction to perform spoofing and session hijacking. Another name for this type of attack is Session Replay.
  • Using Slashes in Alternate Encoding
    This attack targets the encoding of the Slash characters. An attacker would try to exploit common filtering problems related to the use of the slashes characters to gain access to resources on the target host. Directory-driven systems, such as file systems and databases, typically use the slash character to indicate traversal between directories or other container components. For murky historical reasons, PCs (and, as a result, Microsoft OSs) choose to use a backslash, whereas the UNIX world typically makes use of the forward slash. The schizophrenic result is that many MS-based systems are required to understand both forms of the slash. This gives the attacker many opportunities to discover and abuse a number of common filtering problems. The goal of this pattern is to discover server software that only applies filters to one version, but not the other.
nessus via4
  • NASL family SuSE Local Security Checks
    NASL id SUSE_SU-2018-2081-2.NASL
    description This update for xen fixes the following issues : Security issues fixed : CVE-2018-12891: Fix preemption checks bypass in x86 PV MM handling (XSA-264) (bsc#1097521). CVE-2018-12892: Fix libxl failure to honour readonly flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523). CVE-2018-12893: Fix #DB exception safety check that could be triggered by a guest (XSA-265) (bsc#1097522). CVE-2018-11806: Fix heap buffer overflow while reassembling fragmented datagrams (bsc#1096224). CVE-2018-3665: Fix lazy FP Save/Restore (XSA-267) (bsc#1095242). Bug fixes: bsc#1027519: Update to Xen 4.7.6 bug fix only release. bsc#1087289: Xen BUG at sched_credit.c:1663. bsc#1094725: `virsh blockresize` does not work with Xen qdisks. Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen 2019-02-21
    modified 2018-12-01
    plugin id 118277
    published 2018-10-22
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=118277
    title SUSE SLES12 Security Update : xen (SUSE-SU-2018:2081-2)
  • NASL family SuSE Local Security Checks
    NASL id OPENSUSE-2018-803.NASL
    description This update for xen fixes the following issues : Security issues fixed : - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267) (bsc#1095242). - CVE-2018-12891: Fix possible Denial of Service (DoS) via certain PV MMU operations that affect the entire host (XSA-264) (bsc#1097521). - CVE-2018-12892: Fix libxl to honour the readonly flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523). - CVE-2018-12893: Fix crash/Denial of Service (DoS) via safety check (XSA-265) (bsc#1097522). - CVE-2018-11806: Fix heap buffer overflow while reassembling fragmented datagrams (bsc#1096224). Bug fixes : - bsc#1027519: Add upstream patches from January. - bsc#1087289: Fix xen scheduler crash. This update was imported from the SUSE:SLE-12-SP3:Update update project.
    last seen 2019-02-21
    modified 2018-09-06
    plugin id 111565
    published 2018-08-07
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=111565
    title openSUSE Security Update : xen (openSUSE-2018-803)
  • NASL family Misc.
    NASL id XEN_SERVER_XSA-266.NASL
    description According to its self-reported version number, the Xen hypervisor installed on the remote host is affected by a local security bypass vulnerability. Note that Nessus has checked the changeset versions based on the xen.git change log. Nessus did not check guest hardware configurations or if patches were applied manually to the source code before a recompile and reinstall.
    last seen 2019-02-21
    modified 2018-12-07
    plugin id 111381
    published 2018-07-27
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=111381
    title Xen Project Local Security Bypass Vulnerability (XSA-266)
  • NASL family Debian Local Security Checks
    NASL id DEBIAN_DSA-4236.NASL
    description Multiple vulnerabilities have been discovered in the Xen hypervisor : - CVE-2018-12891 It was discovered that insufficient validation of PV MMU operations may result in denial of service. - CVE-2018-12892 It was discovered that libxl fails to honour the 'readonly' flag on HVM-emulated SCSI disks. - CVE-2018-12893 It was discovered that incorrect implementation of debug exception checks could result in denial of service.
    last seen 2019-02-21
    modified 2018-11-13
    plugin id 110787
    published 2018-06-29
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=110787
    title Debian DSA-4236-1 : xen - security update
  • NASL family Gentoo Local Security Checks
    NASL id GENTOO_GLSA-201810-06.NASL
    description The remote host is affected by the vulnerability described in GLSA-201810-06 (Xen: Multiple vulnerabilities) Multiple vulnerabilities have been discovered in Xen. Please review the referenced CVE identifiers for details. Impact : A local attacker could cause a Denial of Service condition or disclose sensitive information. Workaround : There is no known workaround at this time.
    last seen 2019-02-21
    modified 2018-10-31
    plugin id 118506
    published 2018-10-31
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=118506
    title GLSA-201810-06 : Xen: Multiple vulnerabilities (Foreshadow) (Meltdown) (Spectre)
  • NASL family Fedora Local Security Checks
    NASL id FEDORA_2018-A7862A75F5.NASL
    description preemption checks bypassed in x86 PV MM handling [XSA-264, CVE-2018-12891] (#1595959) x86: #DB exception safety check can be triggered by a guest [XSA-265, CVE-2018-12893] (#1595958) libxl fails to honour readonly flag on HVM emulated SCSI disks [XSA-266, CVE-2018-12892] (#1595957) Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen 2019-02-21
    modified 2019-01-03
    plugin id 120682
    published 2019-01-03
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=120682
    title Fedora 28 : xen (2018-a7862a75f5)
  • NASL family SuSE Local Security Checks
    NASL id SUSE_SU-2018-2059-1.NASL
    description This update for xen fixes the following issues: Security issues fixed : - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267) (bsc#1095242). - CVE-2018-12891: Fix possible Denial of Service (DoS) via certain PV MMU operations that affect the entire host (XSA-264) (bsc#1097521). - CVE-2018-12892: Fix libxl to honour the readonly flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523). - CVE-2018-12893: Fix crash/Denial of Service (DoS) via safety check (XSA-265) (bsc#1097522). - CVE-2018-11806: Fix heap buffer overflow while reassembling fragmented datagrams (bsc#1096224). Bug fixes : - bsc#1027519: Add upstream patches from January. - bsc#1087289: Fix xen scheduler crash. Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen 2019-02-21
    modified 2018-12-01
    plugin id 111348
    published 2018-07-26
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=111348
    title SUSE SLED12 / SLES12 Security Update : xen (SUSE-SU-2018:2059-1)
  • NASL family Fedora Local Security Checks
    NASL id FEDORA_2018-1A467757CE.NASL
    description preemption checks bypassed in x86 PV MM handling [XSA-264, CVE-2018-12891] x86: #DB exception safety check can be triggered by a guest [XSA-265, CVE-2018-12893] libxl fails to honour readonly flag on HVM emulated SCSI disks [XSA-266, CVE-2018-12892] ---- Speculative register leakage from lazy FPU context switching [XSA-267, CVE-2018-3665] fix for change in iasl output Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen 2019-02-21
    modified 2018-09-05
    plugin id 111236
    published 2018-07-24
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=111236
    title Fedora 27 : xen (2018-1a467757ce)
  • NASL family SuSE Local Security Checks
    NASL id SUSE_SU-2018-2081-1.NASL
    description This update for xen fixes the following issues: Security issues fixed : - CVE-2018-12891: Fix preemption checks bypass in x86 PV MM handling (XSA-264) (bsc#1097521). - CVE-2018-12892: Fix libxl failure to honour readonly flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523). - CVE-2018-12893: Fix #DB exception safety check that could be triggered by a guest (XSA-265) (bsc#1097522). - CVE-2018-11806: Fix heap buffer overflow while reassembling fragmented datagrams (bsc#1096224). - CVE-2018-3665: Fix lazy FP Save/Restore (XSA-267) (bsc#1095242). Bug fixes : - bsc#1027519: Update to Xen 4.7.6 bug fix only release. - bsc#1087289: Xen BUG at sched_credit.c:1663. - bsc#1094725: `virsh blockresize` does not work with Xen qdisks. Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen 2019-02-21
    modified 2018-12-01
    plugin id 111433
    published 2018-07-30
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=111433
    title SUSE SLES12 Security Update : xen (SUSE-SU-2018:2081-1)
  • NASL family SuSE Local Security Checks
    NASL id SUSE_SU-2018-1981-1.NASL
    description This update for xen fixes the following issues: Security issues fixed : - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267) (bsc#1095242). - CVE-2018-12891: Fix possible Denial of Service (DoS) via certain PV MMU operations that affect the entire host (XSA-264) (bsc#1097521). - CVE-2018-12892: Fix libxl to honour the readonly flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523). - CVE-2018-12893: Fix crash/Denial of Service (DoS) via safety check (XSA-265) (bsc#1097522). Bug fixes : - bsc#1027519: Add upstream patches from January. - bsc#1098403: Fix regression introduced by changes for bsc#1079730. A PV domU without qcow2 and/or vfb has no qemu attached. Ignore QMP errors for PV domUs to handle PV domUs with and without an attached qemu-xen. - bsc#1087289: Fix xen scheduler crash. Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen 2019-02-21
    modified 2019-01-02
    plugin id 120050
    published 2019-01-02
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=120050
    title SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2018:1981-1)
  • NASL family SuSE Local Security Checks
    NASL id OPENSUSE-2018-766.NASL
    description This update for xen fixes the following issues : Security issues fixed : - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267) (bsc#1095242). - CVE-2018-12891: Fix possible Denial of Service (DoS) via certain PV MMU operations that affect the entire host (XSA-264) (bsc#1097521). - CVE-2018-12892: Fix libxl to honour the readonly flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523). - CVE-2018-12893: Fix crash/Denial of Service (DoS) via safety check (XSA-265) (bsc#1097522). Bug fixes : - bsc#1027519: Add upstream patches from January. - bsc#1098403: Fix regression introduced by changes for bsc#1079730. A PV domU without qcow2 and/or vfb has no qemu attached. Ignore QMP errors for PV domUs to handle PV domUs with and without an attached qemu-xen. - bsc#1087289: Fix xen scheduler crash. This update was imported from the SUSE:SLE-15:Update update project.
    last seen 2019-02-21
    modified 2018-09-06
    plugin id 111418
    published 2018-07-30
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=111418
    title openSUSE Security Update : xen (openSUSE-2018-766)
refmap via4
bid 104571
confirm http://xenbits.xen.org/xsa/advisory-266.html
debian DSA-4236
gentoo GLSA-201810-06
mlist [oss-security] 20180627 Xen Security Advisory 266 (CVE-2018-12892) - libxl fails to honour readonly flag on HVM emulated SCSI disks
sectrack 1041203
Last major update 02-07-2018 - 13:29
Published 02-07-2018 - 13:29
Last modified 29-03-2019 - 12:24
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