CVE-2026-42055

Advisory lineage Upstream: 0 Downstream: 3
PUBLISHED
Published: 17 Jun 2026, 14:04
Last modified:18 Jun 2026, 03:57

Vulnerability Summary

Overall Risk (default)
high
70/100
CVSS Score
9.2 CRITICAL
v4.0 (cve.org)
EPSS Score
0.64% LOW
1% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

17 Jun 2026, 14:04
Published
Vulnerability first disclosed
18 Jun 2026, 03:57
Last Modified
Vulnerability information updated

Description

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists when the proxy_http_version to 2 or grpc_pass directives are used to proxy HTTP/2 traffic, the ignore_invalid_headers directive is set to off, and the large_client_header_buffers directive size is larger than 2 megabytes. A remote, unauthenticated attacker, along with conditions beyond their control, could send large headers while creating an upstream request. This may cause a heap-based buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CVSS Metrics

  • v4.0•CRITICAL•Score: 9.2CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
  • v3.1•HIGH•Score: 8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 0.64%• Percentile: 46%

Techniques & Countermeasures

  • CWE-122•Heap-based Buffer Overflow

    A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

Affected Systems

  • f5•nginx open source

    ≥ 1.13.10, < 1.31.2 | ≥ 1.30.2, < 1.30.3

  • f5•nginx plus

    ≥ 37.0, < 37.0.2.1 | ≥ R36, < R36 P6

References (1)