Copeland XWEB 300D PRO: Out-of-bounds Write
CVE-2026-20797 is a critical-severity out-of-bounds write vulnerability in Copeland XWEB 300D PRO from Copeland, 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. Affected Copeland XWEB 300D PRO versions: 1.12.1 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.83% chance of exploitation within 30 days, higher than 58% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of Copeland XWEB 300D PRO you run against the affected versions below, and install the vendor's latest release.
- 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 |
|---|---|---|---|
| Copeland | Copeland XWEB 300D PRO | 1.12.1 and earlier | Not stated |
| Copeland | Copeland XWEB 500D PRO | 1.12.1 and earlier | Not stated |
| Copeland | Copeland XWEB 500B PRO | 1.12.1 and earlier | Not stated |
| Copeland | Xweb 300d Pro Firmware | 1.12.1 and earlier | Not stated |
| Copeland | Xweb 500d Pro Firmware | 1.12.1 and earlier | Not stated |
| Copeland | Xweb 500b Pro Firmware | 1.12.1 and earlier | 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 | 4.3 | Medium | CNA (hq.dhs.gov) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
A stack based buffer overflow exists in an API route of XWEB Pro version 1.12.1 and prior, enabling unauthenticated attackers to cause stack corruption and a termination of the program.
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.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-057-10.jsonThird Party Advisory
- cisa.gov/news-events/ics-advisories/icsa-26-057-10Third Party Advisory, US Government Resource
Other references
Other vulnerabilities in Copeland XWEB 300D PRO
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
Recent Out-of-bounds Write vulnerabilities
- 9.8 Critical severity
- 8.8 High severity
- 8.8 High severity
- 7.1 High severity
- 7.8 High severity
- 9.8 Critical severity
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