CISA KEV Critical
Memory corruption
CVE-2019-5544 — VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow Vulnerability
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.
77
Urgent
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Confirmed exploitation (CISA KEV)+35
- Used in ransomware campaigns (CISA)+10
- Public exploit/PoC (nuclei)+4
- EPSS 97.3% (30-day exploitation probability)+15
- Technical severity (critical)+10
- Automatable exploitation (SSVC)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Exploitation
Confirmed
CISA KEV, listed Nov 3, 2021
EPSS FIRST
97.26%
ahead of 100% of scored CVEs · Oct 14, 2026
Affects
Fedoraproject
Fedora and 15 more
CVSS base
9.8
Critical · 4 source(s)
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Exploitation
Active
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — www.vmware.com (NIST National Vulnerability Database)
CISA required action CISA
Apply updates per vendor instructions.
US federal deadline: May 3, 2022 — passed 1626 day(s) ago
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Fedoraproject Fedora, Openslp Openslp, Red Hat Enterprise Linux Desktop…).
- Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- EPSS ahead of 100% of scored CVEs: prioritize it in the patch queue.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Fedoraproject | Fedora | version 30version 31 | Vulnerable | NIST National Vulnerability Database |
| Openslp | Openslp | ≤ 2.0.0 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux Desktop | version 6.0version 7.0 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux For Ibm Z Systems | version 6.0_s390xversion 7.0_s390x | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux For Ibm Z Systems Eus | version 7.7_s390x | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux For Power Big Endian | version 7.0_ppc64version 6.0_ppc64 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux For Power Big Endian Eus | version 7.7_ppc64 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux For Power Little Endian | version 7.0_ppc64le | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux For Power Little Endian Eus | version 7.7_ppc64le | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux Server | version 6.0version 7.0 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux Server Aus | version 7.7 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux Server Eus | version 7.7 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux Server Tus | version 7.7 | Vulnerable | NIST National Vulnerability Database |
| Red Hat | Enterprise Linux Workstation | version 6.0version 7.0 | Vulnerable | NIST National Vulnerability Database |
| Vmware | Esxi |
version 6.7-670-201911001version 6.7-670-201908221version 6.7-670-201908219version 6.7-670-201908220version 6.5-650-201803001version 6.5-650-201806001version 6.5-650-201808001version 6.5-650-201810001 and 231 moreversion 6.5-650-201810002version 6.5-650-201811001version 6.5-650-201811002version 6.5-650-201811301version 6.5-650-201901001version 6.5-650-201903001version 6.5-650-201905001version 6.5-650-201908001version 6.5-650-201910001version 6.5-650-20191004001version 6.5-650-201911001version 6.5-650-201911401version 6.5-650-201911402version 6.7version 6.7-670-201806001version 6.7-670-201807001version 6.7-670-201808001version 6.7-670-201810001version 6.7-670-201810101version 6.7-670-201810102version 6.7-670-201810103version 6.7-670-201810201version 6.7-670-201810202version 6.7-670-201810203version 6.7-670-201810204version 6.7-670-201810205version 6.7-670-201810206version 6.7-670-201810207version 6.7-670-201810208version 6.7-670-201810209version 6.7-670-201810210version 6.7-670-201810211version 6.7-670-201810212version 6.7-670-201810213version 6.7-670-201810214version 6.7-670-201810215version 6.7-670-201810216version 6.7-670-201810217version 6.7-670-201810218version 6.7-670-201810219version 6.7-670-201810220version 6.7-670-201810221version 6.7-670-201810222version 6.7-670-201810223version 6.7-670-201810224version 6.7-670-201810225version 6.7-670-201810226version 6.7-670-201810227version 6.7-670-201810228version 6.7-670-201810229version 6.7-670-201810230version 6.7-670-201810231version 6.7-670-201810232version 6.7-670-201810233version 6.7-670-201810234version 6.7-670-201811001version 6.7-670-201901001version 6.7-670-201901401version 6.7-670-201901402version 6.7-670-201901403version 6.7-670-201903001version 6.7-670-201904001version 6.7-670-201904201version 6.7-670-201904202version 6.7-670-201904203version 6.7-670-201904204version 6.7-670-201904205version 6.7-670-201904206version 6.7-670-201904207version 6.7-670-201904208version 6.7-670-201904209version 6.7-670-201904210version 6.7-670-201904211version 6.7-670-201904212version 6.7-670-201904213version 6.7-670-201904214version 6.7-670-201904215version 6.7-670-201904216version 6.7-670-201904217version 6.7-670-201904218version 6.7-670-201904219version 6.7-670-201904220version 6.7-670-201904221version 6.7-670-201904222version 6.7-670-201904223version 6.7-670-201904224version 6.7-670-201904225version 6.7-670-201904226version 6.7-670-201904227version 6.7-670-201904228version 6.7-670-201904229version 6.7-670-201905001version 6.7-670-201906002version 6.7-670-201908101version 6.7-670-201908102version 6.7-670-201908103version 6.7-670-201908104version 6.7-670-201908201version 6.7-670-201908202version 6.7-670-201908203version 6.7-670-201908204version 6.7-670-201908205version 6.7-670-201908206version 6.7-670-201908207version 6.7-670-201908208version 6.7-670-201908209version 6.7-670-201908210version 6.7-670-201908211version 6.7-670-201908212version 6.7-670-201908213version 6.7-670-201908214version 6.7-670-201908215version 6.7-670-201908216version 6.7-670-201908217version 6.7-670-201908218version 6.0version 6.0-1version 6.0-1aversion 6.0-1bversion 6.0-2version 6.0-3version 6.0-3aversion 6.0-600-201504401version 6.0-600-201505401version 6.0-600-201507101version 6.0-600-201507102version 6.0-600-201507401version 6.0-600-201507402version 6.0-600-201507403version 6.0-600-201507404version 6.0-600-201507405version 6.0-600-201507406version 6.0-600-201507407version 6.0-600-201509101version 6.0-600-201509102version 6.0-600-201509201version 6.0-600-201509202version 6.0-600-201509203version 6.0-600-201509204version 6.0-600-201509205version 6.0-600-201509206version 6.0-600-201509207version 6.0-600-201509208version 6.0-600-201509209version 6.0-600-201509210version 6.0-600-201510401version 6.0-600-201511401version 6.0-600-201601101version 6.0-600-201601102version 6.0-600-201601401version 6.0-600-201601402version 6.0-600-201601403version 6.0-600-201601404version 6.0-600-201601405version 6.0-600-201602401version 6.0-600-201603101version 6.0-600-201603102version 6.0-600-201603201version 6.0-600-201603202version 6.0-600-201603203version 6.0-600-201603204version 6.0-600-201603205version 6.0-600-201603206version 6.0-600-201603207version 6.0-600-201603208version 6.0-600-201605401version 6.0-600-201608101version 6.0-600-201608401version 6.0-600-201608402version 6.0-600-201608403version 6.0-600-201608404version 6.0-600-201608405version 6.0-600-201610410version 6.0-600-201611401version 6.0-600-201611402version 6.0-600-201611403version 6.0-600-201702101version 6.0-600-201702102version 6.0-600-201702201version 6.0-600-201702202version 6.0-600-201702203version 6.0-600-201702204version 6.0-600-201702205version 6.0-600-201702206version 6.0-600-201702207version 6.0-600-201702208version 6.0-600-201702209version 6.0-600-201702210version 6.0-600-201702211version 6.0-600-201702212version 6.0-600-201703401version 6.0-600-201706101version 6.0-600-201706102version 6.0-600-201706103version 6.0-600-201706401version 6.0-600-201706402version 6.0-600-201706403version 6.0-600-201710301version 6.0-600-201811001version 6.0-600-201811401version 6.5version 6.5-650-201701001version 6.5-650-201703001version 6.5-650-201703002version 6.5-650-201704001version 6.5-650-201707101version 6.5-650-201707102version 6.5-650-201707103version 6.5-650-201707201version 6.5-650-201707202version 6.5-650-201707203version 6.5-650-201707204version 6.5-650-201707205version 6.5-650-201707206version 6.5-650-201707207version 6.5-650-201707208version 6.5-650-201707209version 6.5-650-201707210version 6.5-650-201707211version 6.5-650-201707212version 6.5-650-201707213version 6.5-650-201707214version 6.5-650-201707215version 6.5-650-201707216version 6.5-650-201707217version 6.5-650-201707218version 6.5-650-201707219version 6.5-650-201707220version 6.5-650-201707221version 6.5-650-201710001version 6.5-650-201712001 |
Vulnerable | NIST National Vulnerability Database |
| Vmware | Horizon Daas | ≥ 8.0.0 and < 9.0.0.0 | Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 9.8 | CVSS 3.1 | Critical | 3.9 | 5.9 | nvd@nist.gov via NIST National Vulnerability Database |
| 9.8 | CVSS 3.1 | Critical | 3.9 | 5.9 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database |
| 9.8 | CVSS 3.1 | Critical | — | — | GitHub, Inc. via GitHub Security Advisories |
| 9.8 | CVSS 3.1 | Critical | — | — | CISA-ADP via CVE Program (cve.org) e CISA ADP |
| 7.5 | CVSS 2.0 | High | 10.0 | 6.4 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
CISA KEV details CISA
CISA lists a CVE once it has evidence of exploitation against real targets.
Listed
Nov 3, 2021
Federal deadline
May 3, 2022
passed 1626 day(s) ago
Ransomware use
Known
CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.
Public exploits, PoCs and detection templates
Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.
Detection templates (Nuclei)
Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 97.26%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
- Hunt retroactively in logs from before Nov 3, 2021 (KEV listing): exploitation may have started earlier.
Timeline
What happened to this CVE, newest first.
- 2026
- SSVC assessment updated
- Record published
- Fix documented
- Affected products added · vmware/horizon daas, vmware/esxi, redhat/enterprise linux desktop, redhat/enterprise linux for ibm z systems, redhat/ent
- CVSS changed · 9.8
- Source status changed · → Analyzed
- Added to CISA KEV (detected)
- Record created in this database
- 2021
- Added to CISA KEV catalog
- 2019
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 13, 2026 – Oct 13, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
15 on the record
- www.vmware.com/security/advisories/VMSA-2019-0022.html
- www.cisa.gov/known-exploited-vulnerabilities-catalog
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DA3L
- github.com/advisories/GHSA-4734-5452-r5fh
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZPXXJZ
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DA3LYA
- access.redhat.com/errata/RHSA-2019:4240
- security.gentoo.org/glsa/202005-12
- www.openwall.com/lists/oss-security/2019/12/10/2
- access.redhat.com/errata/RHSA-2020:0199
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPXX
- nvd.nist.gov/vuln/detail/CVE-2019-5544
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DA3L
- www.openwall.com/lists/oss-security/2019/12/11/2
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPXX
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-59849 Infinite Loop in Libssh Jul 21, 2026
- Medium CVE-2026-59842 Out-of-bounds Read in Libssh Jul 21, 2026
- High CVE-2026-15370 Stack-based Buffer Overflow in Libssh Jul 21, 2026
- High CVE-2026-54230 Abrt: event handler scripts follow symlinks when writing output files, allowing arbitrary file overwrites Jun 13, 2026
- Medium CVE-2026-54231 Abrt: unsanitized systemd journal content written to dump directory files enables content injection Jun 13, 2026
- High CVE-2026-42009 Gnutls: gnutls: denial of service via dtls packet reordering vulnerability May 18, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2019-5544 is "VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow Vulnerability", rated Critical. It affects Fedora (Fedoraproject); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 9.8 describes technical severity. EPSS 97.26% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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