High

NGINX upstream TLS MITM plaintext response injection

IdentifiersCVE-2026-1642CWE-349· Acceptance of Extraneous Untrusted…

CVE-2026-1642 is a vulnerability in NGINX Open Source and NGINX Plus when they are configured to proxy requests to upstream TLS servers. Under affected versions, an attacker who can obtain a man-in-the-middle position on the network path between NGINX and the upstream TLS backend may be able, under additional conditions beyond the attacker’s control, to inject plaintext data into the response returned by the upstream proxied server. The issue affects deployments using NGINX as a reverse proxy toward TLS-enabled upstream services, including contexts such as HTTP/1.x, HTTP/2, gRPC, and uWSGI as described in vendor advisory material. Reported affected NGINX Open Source versions are 1.3.0 through 1.29.4; fixed versions include 1.29.5 and 1.28.2 on the supported branches.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can compromise response integrity by causing NGINX to forward attacker-injected plaintext content to downstream clients in place of, or mixed with, legitimate upstream response data. Depending on the proxied application and trust assumptions, this may enable content tampering, delivery of attacker-controlled data to clients, and secondary application-layer impacts. The available information describes injection into proxied responses rather than direct server-side code execution on the NGINX host.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure by eliminating opportunities for man-in-the-middle interception on the upstream side. Place upstream TLS backends on trusted and segmented network paths, enforce strict upstream certificate validation, maintain sound PKI hygiene, and prefer mutually authenticated TLS or equivalent authenticated private connectivity where feasible. Avoid proxying to upstream TLS services across untrusted or weakly controlled network segments until fixed versions are deployed.

Remediation

Patch, then assume compromise.

Upgrade NGINX Open Source to a fixed release, specifically 1.29.5 or later on the mainline branch, or 1.28.2 or later on the stable branch. For NGINX Plus, upgrade to the vendor-fixed patch levels identified for affected releases, including R36 P2, R35 P1, or R32 P4 as applicable. For downstream products that embed vulnerable NGINX components, deploy a product release that incorporates the fixed NGINX version. End-of-Technical-Support versions should be retired and replaced with supported fixed releases.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

F5Nginxapplication

F5Nginx Gateway Fabricapplication

F5Nginx Ingress Controllerapplication

F5Nginx Instance Managerapplication

F5Nginx Open Sourceapplication

F5Nginx Open Source (Oss)application

F5Nginx Plusapplication

NginxNginxapplication

NginxNginx Plusapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

24 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

24 SOURCESView more in app

zeropath blogNews

Jun 17, 2026

NGINX HTTP/3 QPACK Use After Free (CVE-2026-42530): Brief Summary of a Critical Remote Vulnerability - ZeroPath Blog | ZeroPath

An NGINX-related SSL upstream MITM injection vulnerability mentioned only as part of vendor security history.

the hacker newsNews

Feb 9, 2026

⚡ Weekly Recap: AI Skill Malware, 31Tbps DDoS, Notepad++ Hack, LLM Backdoors and More

Unknown (listed as a trending CVE affecting F5 NGINX OSS and NGINX Plus; no technical details provided in the content).

the hacker newsNews

Feb 9, 2026

⚡ Weekly Recap: AI Skill Malware, 31Tbps DDoS, Notepad++ Hack, LLM Backdoors and More

Unknown (listed as a trending CVE affecting F5 NGINX OSS and NGINX Plus; no technical details provided in the content).

the hacker newsNews

Feb 9, 2026

⚡ Weekly Recap: AI Skill Malware, 31Tbps DDoS, Notepad++ Hack, LLM Backdoors and More

Unknown (listed as a trending CVE affecting F5 NGINX OSS and NGINX Plus; no technical details provided in the content).

+1 more in the timeline

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity13