CVE-2026-42934

NGINX ngx_http_charset_module vulnerability

Assigner: f5
Reserved: 30.04.2026 Published: 13.05.2026 Updated: 13.05.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
CVSS Score: 4.8

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	Low
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	Low

CVSS 3.1

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
CVSS Score: 6.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	Low	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	Present	Availability	Low	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	F5
Product	NGINX Plus
Versions	Default: unknown unaffected from R37 to * (excl.) affected from R36 to R36 P4 (excl.) affected from R32 to R32 P6 (excl.)

Vendor

Product

NGINX Plus

Versions

Default: unknown

unaffected from R37 to * (excl.)
affected from R36 to R36 P4 (excl.)
affected from R32 to R32 P6 (excl.)

Vendor	F5
Product	NGINX Open Source
Versions	Default: unaffected unaffected from 1.31.0 to * (excl.) affected from 0.3.50 to 1.30.1 (excl.)

Vendor

Product

NGINX Open Source

Versions

Default: unaffected

unaffected from 1.31.0 to * (excl.)
affected from 0.3.50 to 1.30.1 (excl.)

Credits

F5 acknowledges David Carlier and Zhenpeng (Leo) Lin of depthfirst for bringing this issue to our attention and following the highest standards of coordinated disclosure. finder

References

Problem Types