CVE-2021-34584
CODESYS V2 web server: crafted requests could trigger a buffer over-read (DoS)
Crafted web server requests can be utilised to read partial stack or heap memory or may trigger a denial-of- service condition due to a crash in the CODESYS V2 web server prior to V1.1.9.22.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
CODESYS V2 web server: crafted requests could trigger a buffer over-read (DoS)
Crafted web server requests can be utilised to read partial stack or heap memory or may trigger a denial-of- service condition due to a crash in the CODESYS V2 web server prior to V1.1.9.22.
- Record
CVE-2021-34584- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H - Weakness
- CWE-126
- Updated
- 2026-11-02
EUVDEUVD-2021-21234
Crafted web server requests can be utilised to read partial stack or heap memory or may trigger a denial-of- service condition due to a crash in the CODESYS V2 web server prior to V1.1.9.22.
- Record
EUVD-2021-21234- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-j5c2-6xq9-fj5m
Crafted web server requests can be utilised to read partial stack or heap memory or may trigger a...
Crafted web server requests can be utilised to read partial stack or heap memory or may trigger a denial-of- service condition due to a crash in the CODESYS V2 web server prior to V1.1.9.22.
- Record
GHSA-j5c2-6xq9-fj5m- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H - Weakness
- CWE-126
- Updated
- 2026-11-02
NVD
Crafted web server requests can be utilised to read partial stack or heap memory or may trigger a denial-of- service condition due to a crash in the CODESYS V2 web server prior to V1.1.9.22.
- Record
CVE-2021-34584- CVSS 3.1
- 9.1 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H - CVSS 2.0
- 6.4 Medium
AV:N/AC:L/Au:N/C:P/I:N/A:P - Weakness
- CWE-126
- Updated
- 2026-11-02
Affected products
- codesys
- codesys v2
- wago 750-8202 firmware
- wago 750-8203 firmware
- wago 750-8204 firmware
- wago 750-8206 firmware
- wago 750-8207 firmware
- wago 750-8208 firmware
- wago 750-8210 firmware
- wago 750-8211 firmware
- wago 750-8212 firmware
- wago 750-8213 firmware
Show 17 moreShow less
- wago 750-8214 firmware
- wago 750-8216 firmware
- wago 750-8217 firmware
- wago 750-823 firmware
- wago 750-829 firmware
- wago 750-831 firmware
- wago 750-832 firmware
- wago 750-852 firmware
- wago 750-862 firmware
- wago 750-880 firmware
- wago 750-881 firmware
- wago 750-882 firmware
- wago 750-885 firmware
- wago 750-889 firmware
- wago 750-890 firmware
- wago 750-891 firmware
- wago 750-893 firmware
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-34584 is a critical vulnerability (CVSS 9.1) in Codesys, published October 26, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.08%, the 65th percentile. No source names a fixed version.