Vulnerability · Published May 13, 2026 · Assigned by f5

CVE-2026-42934NGINX ngx_http_charset_module vulnerability

Medium 4.8

In plain English

A medium-severity out-of-bounds read in NGINX Open Source from F5. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 54% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.8Medium

Exploit odds (30 days)0.7%top 45.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_charset_module module. When charset, source_charset, and charset_map and proxy_pass with disabled buffering ("off") directives are configured, unauthenticated attackers can send requests that with conditions beyond the attackers' 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Alpine:v3.21	nginx	1.26.3-r1	ALPINE-CVE-2026-42934
Alpine:v3.22	nginx	1.28.3-r1	ALPINE-CVE-2026-42934
Alpine:v3.23	nginx	1.28.3-r1	ALPINE-CVE-2026-42934
Alpine:v3.24	nginx	1.30.1-r0	ALPINE-CVE-2026-42934
Debian:12	nginx	1.22.1-9+deb12u7	DEBIAN-CVE-2026-42934
Debian:13	nginx	1.26.3-3+deb13u5	DEBIAN-CVE-2026-42934
Debian:14	nginx	1.30.0-4	DEBIAN-CVE-2026-42934
Ubuntu:22.04:LTS	nginx	1.18.0-6ubuntu14.12	UBUNTU-CVE-2026-42934
Ubuntu:24.04:LTS	nginx	1.24.0-2ubuntu7.9	UBUNTU-CVE-2026-42934
Ubuntu:25.10	nginx	1.28.0-6ubuntu1.4	UBUNTU-CVE-2026-42934
Ubuntu:26.04:LTS	nginx	1.28.3-2ubuntu1.2	UBUNTU-CVE-2026-42934

Affected products (as reported)

Vendor	Product	Versions
F5	NGINX Plus	R36 – before R36 P4R32 – before R32 P6
F5	NGINX Open Source	0.3.50 – before 1.30.1

Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

References

https://my.f5.com/manage/s/article/K000161028 vendor-advisory, patch