CVE-2019-5544Exploited in the wildNVD status: Analyzed
VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow
CVE-2019-5544 is a critical-severity out-of-bounds write vulnerability in ESXi and Horizon DaaS, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild, including in ransomware campaigns.
Patch now
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Horizon Daas to 9.0.0.0 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on vmware.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| ESXi and Horizon DaaS | ESXi and Horizon DaaS | Not specified in the record | Not stated |
| VMware | Horizon Daas | 8.0.0 up to, but not including, 9.0.0.0 | 9.0.0.0 |
| VMware | Esxi | 6.0; 6.5; 6.7 | Not stated |
| Red Hat | Enterprise Linux Desktop | 6.0; 7.0 | Not stated |
| Red Hat | Enterprise Linux For IBM Z Systems | 6.0_s390x; 7.0_s390x | Not stated |
| Red Hat | Enterprise Linux For IBM Z Systems EUS | 7.7_s390x | Not stated |
| Red Hat | Enterprise Linux For Power Big Endian | 6.0_ppc64; 7.0_ppc64 | Not stated |
| Red Hat | Enterprise Linux For Power Big Endian EUS | 7.7_ppc64 | Not stated |
| Red Hat | Enterprise Linux For Power Little Endian | 7.0_ppc64le | Not stated |
| Red Hat | Enterprise Linux For Power Little Endian EUS | 7.7_ppc64le | Not stated |
| Red Hat | Enterprise Linux Server | 6.0; 7.0 | Not stated |
| Red Hat | Enterprise Linux Server AUS | 7.7 | Not stated |
| Red Hat | Enterprise Linux Server EUS | 7.7 | Not stated |
| Red Hat | Enterprise Linux Server TUS | 7.7 | Not stated |
| Red Hat | Enterprise Linux Workstation | 6.0; 7.0 | Not stated |
| Openslp | Openslp | 2.0.0 and earlier | Not stated |
| Fedora Project | Fedora | 30; 31 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 3.1 | 9.8 | Critical | CISA (ADP) |
| CVSS 2.0 | 7.5 | High | NVD |
Official description
OpenSLP as used in ESXi and the Horizon DaaS appliances has a heap overwrite issue. VMware has evaluated the severity of this issue to be in the Critical severity range with a maximum CVSSv3 base score of 9.8.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Third-party and government advisories
- openwall.com/lists/oss-security/2019/12/10/2Mailing List, Third Party Advisory
- openwall.com/lists/oss-security/2019/12/11/2Mailing List, Third Party Advisory
- access.redhat.com/errata/RHSA-2019:4240Third Party Advisory
- access.redhat.com/errata/RHSA-2020:0199Third Party Advisory
- security.gentoo.org/glsa/202005-12Third Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-5544US Government Resource
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