Public proof of conceptFix available

CVE-2026-42055

Q: Is CVE-2026-42055 actively exploited?

Active exploitation of CVE-2026-42055 has not been confirmed. Its EPSS score was 6.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-42055?

CVE-2026-42055 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

A public proof of concept exists; no exploitation attested.

Published2026-06-17
WeaknessCWE-122 · CWE-131 · CWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2026-06-1715:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 15:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-42055?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-42055?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

F5 nginx ingress controller

Branch	Affected	Fixed in	Source
3.x	≥ 3.5.0, ≤ 3.7.2	no fix published	NVD
4.0	≥ 4.0.0, ≤ 4.0.1	no fix published	NVD
5.x	≥ 5.0.0, ≤ 5.5.0	no fix published	NVD

F5 nginx plus

Branch	Affected	Fixed in	Source
—	≥ r33, < r36	r36	NVD
37.0	≥ 37.0.0.1, < 37.0.2.1	37.0.2.1	NVD
—	= r36	no fix published	NVD

F5 waf

Branch	Affected	Fixed in	Source
4.x	≥ 4.10.0, ≤ 4.16.0	no fix published	NVD
5.x	≥ 5.2.0, ≤ 5.8.0	no fix published	NVD
5.x	≥ 5.9.0, ≤ 5.13.1	no fix published	NVD

11 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

nginxAlmaLinux:10all versions · fixed in 2:1.26.3-6.el10_2.5and 9 other packages
nginxAlmaLinux:9all versions · fixed in 2:1.26.3-9.module_el9.8.0+281+75d5e6d4.2and 9 other packages
nginxAlmaLinux:8all versions · fixed in 1:1.24.0-3.module_el8.10.0+4215+c88f2fa5.3.alma.1and 8 other packages

Vendor advisories

CVE-2026-42055 Red Hat Product Security402 products fixed · 1 known affected
nginx: NGINX: Arbitrary code execution or Denial of Service via heap-based buffer overflow with crafted HTTP/2 headers
odf4/odf-console-rhel9 as a component of Red Hat Openshift Data Foundation 4
RHSA-2026:58981 Red Hat Product Security2 products fixed
Red Hat Security Advisory: Red Hat Update Infrastructure 5.3 Technology Preview security update
RHSA-2026:46836 Red Hat Product Security2 products fixed
Red Hat Security Advisory: A Subscription Management tool for finding and reporting Red Hat product usage
RHSA-2026:44481 Red Hat Product Security3 products fixed
Red Hat Security Advisory: Red Hat Update Infrastructure 5.2 security update
RHSA-2026:38847 Red Hat Product Security59 products fixed
Red Hat Security Advisory: nginx:1.24 security, bug fix, and enhancement update
RHSA-2026:36639 Red Hat Product Security67 products fixed
Red Hat Security Advisory: nginx:1.26 security, bug fix, and enhancement update

4 more advisories

Full record on NVD

Fix

Vendor fix Red Hat Product Security RHSA-2026:58981 · 2 productsPlease consult the RHUI Technology Preview Release Notes at https://access.redhat.com/articles/7141172 for instructions on how to use this image set.
Vendor fix Red Hat Product Security RHSA-2026:46836 · 2 productsThe containers required to run Discovery can be installed through discovery-installer RPM. See the official documentation for more details.
Vendor fix Red Hat Product Security RHSA-2026:44481 · 3 productsThe container images provided by this release, apart from the installer, should be deployed using rhui-installer utility. See the official documentation for more details.
Vendor fix Red Hat Product Security RHSA-2026:38847 · 59 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
Vendor fix Red Hat Product Security RHSA-2026:27197 · 25 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
Workaround from the vendor Red Hat Product Security RHSA-2026:58981 · 4 productsTo mitigate this vulnerability, ensure that the `ignore_invalid_headers` directive is set to `on` in your NGINX configuration, or reduce the size specified by the `large_client_header_buffers` directive to 2 megabytes or less. These changes require an NGINX service reload or restart to take effect.…

Advisories and patches

my.f5.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedHORKimhab/CVE-2026-42055

Sources

CISA-ADPSSVC decisionnone2026-06-17
OpenCVESSVC decisionnone—
CNACVSS 4.09.2read 2026-10-23
CNACVSS 3.18.1read 2026-10-23
CNAweakness (CWE)CWE-122, CWE-131read 2026-10-23
NVDweakness (CWE)CWE-787read 2026-10-23
FIRST EPSSEPSS score6.5 %2026-10-22
PoC-in-GitHubproof of concept1—
OSVaffected packages—
Microsoft MSRCadvisory—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 4.0 vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Published: 2026-06-17
Last Modified: 2026-09-14
NVD status: Modified
MSRC Title: NGINX ngx_http_proxy_v2_module and ngx_http_grpc_module vulnerability

Frequently asked questions

What is CVE-2026-42055?

Is CVE-2026-42055 actively exploited?

Active exploitation of CVE-2026-42055 has not been confirmed. Its EPSS score was 6.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-42055?

CVE-2026-42055 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

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