CVE-2026-1642: F5 NGINX Open Source · Acceptance of Extraneous Untrusted Data With Trusted Data
Affects F5 NGINX Open SourceSource CVE Database V5
Not known to be exploited · CVSS 5.9 Medium : upgrade to 1.28.2 when convenient.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.28.2
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 4 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade F5 NGINX Open Source to 1.28.2.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| F5NGINX Open Source | Affected
| Fixed in
|
| F5NGINX Plus | Affected
| Fixed in– |
AI-suggested
If you cannot patch yet, consider reviewing proxy configurations and network security controls to limit man-in-the-middle opportunities on upstream connections.
Description
CVE-2026-1642 is a medium severity vulnerability in F5 NGINX Open Source (version 1.3.0) when configured to proxy to upstream TLS servers. An attacker positioned as a man-in-the-middle on the upstream server side may, under certain conditions beyond their control, inject plain text data into the response from the upstream proxied server. This vulnerability involves acceptance of extraneous untrusted data alongside trusted data (CWE-349).