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VulnerabilityPublished

CVE-2026-1642: F5 NGINX Open Source · Acceptance of Extraneous Untrusted Data With Trusted Data

Affects F5 NGINX Open SourceSource CVE Database V5

0

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

CVSS 3.1 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.
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:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 4 Feb 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
F5NGINX Open SourceAffected
  • >=1.3.0 <1.28.2
Fixed in
  • 1.28.2
F5NGINX PlusAffected
  • >=R34
  • >=R33
  • =R36
  • =R35
  • =R32
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).

References

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