The CMsgReader::readRect function in the VNC Viewer component in RealVNC VNC Free Edition 4.0 through 4.1.2, Enterprise Edition E4.0 through
The CMsgReader::readRect function in the VNC Viewer component in RealVNC VNC Free Edition 4.0 through 4.1.2, Enterprise Edition E4.0 through E4.4.2, and Personal Edition P4.0 through P4.4.2 allows remote VNC servers to execute arbitrary code via crafted RFB protocol data, related to "encoding type."
- Published
- Jan 16, 2009
- Updated
- Jun 16, 2026
- EPSS
- 4.1% · 90th percentile
- CWE
- CWE-20
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Report tools
Action score
41
Plan
Add it to your regular patch cycle.
- CVSS
- 40 / 40 · 10.0 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 4.1%
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| realvnc | realvnc | cpe:2.3:a:realvnc:realvnc |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- realvnc realvnc4.0
- realvnc realvnc4.1.2
- realvnc realvnc4.4.2
- realvnc realvnce4.0
- realvnc realvncp4.0
- realvnc realvncp4.4.2
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:10 | vnc4 | before 4.1.1+X4.3.0-31 | 4.1.1+X4.3.0-31 |
| Debian:4.0 | vnc4 | before 4.1.1+X4.3.0-21+etch1 | 4.1.1+X4.3.0-21+etch1 |
| Red Hat:enterprise_linux:3::as | vnc | before 0:4.0-0.beta4.1.8 | 0:4.0-0.beta4.1.8 |
| Red Hat:enterprise_linux:3::as | vnc-debuginfo | before 0:4.0-0.beta4.1.8 | 0:4.0-0.beta4.1.8 |
| Red Hat:enterprise_linux:3::as | vnc-server | before 0:4.0-0.beta4.1.8 | 0:4.0-0.beta4.1.8 |
| Red Hat:enterprise_linux:4::as | vnc | before 0:4.0-12.el4_7.1 | 0:4.0-12.el4_7.1 |
| Red Hat:enterprise_linux:4::as | vnc-debuginfo | before 0:4.0-12.el4_7.1 | 0:4.0-12.el4_7.1 |
| Red Hat:enterprise_linux:4::as | vnc-server | before 0:4.0-12.el4_7.1 | 0:4.0-12.el4_7.1 |
| Red Hat:enterprise_linux:5::client | vnc | before 0:4.1.2-14.el5_3.1 | 0:4.1.2-14.el5_3.1 |
| Red Hat:enterprise_linux:5::client | vnc-debuginfo | before 0:4.1.2-14.el5_3.1 | 0:4.1.2-14.el5_3.1 |
| Red Hat:enterprise_linux:5::client | vnc-server | before 0:4.1.2-14.el5_3.1 | 0:4.1.2-14.el5_3.1 |
Same product
realvnc: all recordsOther highest-scoring records for the same primary product.
- CVE-2013-6886RealVNC VNC 5.0.6 on Mac OS X, Linux, and UNIX allows local users to gain privileges via a crafted argument to the (1) vncserver, (2) vncser28Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:vnc4 | 4.1.1+X4.3.0-31 · Debian:10 | Package registry (OSV) |
| red hat:vnc | 0:4.0-0.beta4.1.8 · Red Hat:enterprise_linux:3::as | Package registry (OSV) |
| red hat:vnc-debuginfo | 0:4.0-0.beta4.1.8 · Red Hat:enterprise_linux:3::as | Package registry (OSV) |
| red hat:vnc-server | 0:4.0-0.beta4.1.8 · Red Hat:enterprise_linux:3::as | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- C · data can be read
- Integrity
- C · data or configuration can be modified
- Availability
- C · the service can be disrupted
- Attack complexity
- Low
- Confidentiality impact
- C
- Integrity impact
- C
- Availability impact
- C
Weakness class (CWE)
CWE-20 · Improper Input ValidationCVSS vector
AV:N/AC:L/Au:N/C:C/I:C/A:C
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Buffer Overflow via Environment VariablesCAPEC-10likelihood: High · High
- Server Side Include (SSI) InjectionCAPEC-101likelihood: High · High
- Cross Zone ScriptingCAPEC-104likelihood: Medium · High
- Command Line Execution through SQL InjectionCAPEC-108likelihood: Low · Very High
- Object Relational Mapping InjectionCAPEC-109likelihood: Low · High
- SQL Injection through SOAP Parameter TamperingCAPEC-110likelihood: High · Very High
- Double EncodingCAPEC-120likelihood: Low · Medium
- Subverting Environment Variable ValuesCAPEC-13likelihood: High · Very High
ATT&CK techniques
- Obfuscated Files or InformationT1027
- Masquerading: Invalid Code SignatureT1036.001
- Steal Web Session CookieT1539
- Subvert Trust Controls: Code SigningT1553.002
- Impair Defenses:Impair Command History LoggingT1562.003
- Hijack Execution Flow:Dynamic Linker HijackingT1574.006
- Hijack Execution Flow:Path Interception by PATH Environment VariableT1574.007
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- secunia.com/advisories/32317
- secunia.com/advisories/33689
- secunia.com/advisories/34184
- sunsolve.sun.com/search/document.do?assetkey=1-21-140455-01-1
- sunsolve.sun.com/search/document.do?assetkey=1-26-248526-1
- www.gentoo.org/security/en/glsa/glsa-200903-17.xml
- www.realvnc.com/pipermail/vnc-list/2008-November/059432.html
- www.realvnc.com/products/free/4.1/release-notes.html
- www.realvnc.com/products/upgrade.html
- www.redhat.com/support/errata/RHSA-2009-0261.html
- www.securityfocus.com/bid/31832
- www.securityfocus.com/bid/33263
- www.vupen.com/english/advisories/2008/2868
- exchange.xforce.ibmcloud.com/vulnerabilities/45969
- exchange.xforce.ibmcloud.com/vulnerabilities/47937
- oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9367
- www.redhat.com/archives/fedora-package-announce/2009-January/msg01025.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.