# CVE-2026-48142 — F5 NGINX Open Source

> As of 2026-06-17, CVE-2026-48142 is a MEDIUM-severity vulnerability in F5 NGINX Open Source, CVSS v3.1 4.8, EPSS 0.3% (29.1th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-48142, most recently “F5 Out-of-Band Patches for Critical NGINX HTTP/3 Use-After-Free and Proxy/gRPC Heap Overflow (CVE-2026-42530, CVE-2026-42055) plus NGINX Gateway Fabric Config Injection (CVE-2026-11311, CVE-2026-50107)”.

**Last updated:** 2026-06-17

## What is CVE-2026-48142?

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_charset_module module. When content is served or proxied through a location block with both source_charset utf-8; and a charset directive (for example, charset koi8-r;) configured, remote, unauthenticated attackers can send requests (in conjunction with conditions beyond their control) to cause a heap buffer over-read in the NGINX worker process, leading to limited disclosure of memory or a restart. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

The record classifies CVE-2026-48142 under weakness class [CWE-125](https://intel.threadlinqs.com/cwe/CWE-125). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction. 2 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 132 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 4.8 — MEDIUM (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L`)
- **CVSS v4.0 base score:** 6.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 29.1% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.6/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-06-17

## Is CVE-2026-48142 being exploited?

It currently carries a trending score of 14 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [F5](https://intel.threadlinqs.com/vendors/f5): NGINX Open Source, NGINX Plus

## How to fix CVE-2026-48142

No vendor patch reference has been recorded for CVE-2026-48142 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-48142

1 tracked threat in the Threadlinqs corpus references CVE-2026-48142, either in the campaign’s CVE list or as an indicator on the campaign record.

- [F5 Out-of-Band Patches for Critical NGINX HTTP/3 Use-After-Free and Proxy/gRPC Heap Overflow (CVE-2026-42530, CVE-2026-42055) plus NGINX Gateway Fabric Config Injection (CVE-2026-11311, CVE-2026-50107)](https://intel.threadlinqs.com/threat/TL-2026-0848) — CRITICAL · 2026-06-18

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10.

**Vendor advisory and patch**

- [my.f5.com — vendor advisory](https://my.f5.com/manage/s/article/K000161585)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-48142
Full detection coverage and IOCs for threats exploiting CVE-2026-48142 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp