CVE-2026-42530

CRITICAL 9.2

Published 2026-06-17 · Last modified 2026-07-16

NGINX Open Source has a vulnerability in the ngx_http_v3_module module. When NGINX Open Source is configured to use the HTTP/3 QUIC module, a remote unauthenticated attacker along with conditions beyond their control can use a specially crafted HTTP/3 session to reopen a QPACK encoder stream. This may cause a Use-after-Free 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.

ELEVATED IMPACT

Severe if exploited (CVSS 9.2), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

3.2%chance of exploitation in 30 days · 87th percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

9.2CVSS 4.0 · CRITICAL

ConfidentialityHigh
IntegrityHigh
AvailabilityHigh

What an attacker needs

✓Access: Reachable over the network — no local access needed
✓Privileges: No account or privileges required
✓User interaction: No user interaction needed
⚠Complexity: Needs a race window or specific setup
✓Requirements: No special attack requirements

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

github-search Search GitHub for public PoC repos

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-42530/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-42530/poc.json

Affected

Vendors F5 Red Hat

Products Nginx Open Source Red Hat Hardened Images Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Lightspeed Proxy 1 Nginx Gateway Fabric Nginx Ingress Controller Nginx Instance Manager

Weakness (CWE)

CWE-416: Use After Free

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Known Affected Software Configurations

Vendor	Product	Version range
F5	Nginx Gateway Fabric	≥ 1.3.0 and ≤ 1.6.2
F5	Nginx Gateway Fabric	≥ 2.0.0 and < 2.6.4
F5	Nginx Ingress Controller	≥ 3.5.0 and ≤ 3.7.2
F5	Nginx Ingress Controller	≥ 5.0.0 and < 5.5.1
F5	Nginx Ingress Controller	4.0.0
F5	Nginx Ingress Controller	4.0.1
F5	Nginx Instance Manager	≥ 2.17.0 and ≤ 2.22.0
F5	Nginx Open Source	≥ 1.31.0 and < 1.31.2

All CVSS metrics

HIGH 8.1 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CRITICAL 9.2 v4.0 · CNA Primary
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
HIGH 8.1 v3.1 · ADP Primary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CRITICAL 9.2 v4.0 · NVD Secondary
CVSS:4.0/AV:N/AC:H/AT:N/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
HIGH 8.1 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References

Advisories

https://my.f5.com/manage/s/article/K000161616 vendor-advisoryVendor Advisory
https://access.redhat.com/security/cve/CVE-2026-42530 vdb-entryx_refsource_REDHATThird Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2489872 issue-trackingx_refsource_REDHATThird Party Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42530.json x_sadp-csaf-vexThird Party Advisory
https://access.redhat.com/errata/RHSA-2026:20351 vendor-advisoryx_refsource_REDHAT

Sources: NVD · CVE.org · EPSS