Is CVE-2026-9256 being actively exploited?

CVE-2026-9256 is not currently listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

What is the CVSS score for CVE-2026-9256?

CVE-2026-9256 has a CVSS 3.1 base score of 8.1 (HIGH).

CVE-2026-9256

HIGH · CVSS 8.1EPSS 2.7%EU EUVD

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap 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.

Key facts

CVSS score: 8.1 (v3.1)
Severity: HIGH
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-122
EPSS score: 2.7% (86th percentile)
In CISA KEV: No
In EU EUVD: Yes (EUVD-2026-31444)
Published: May 22, 2026
NVD last modified: August 25, 2026
Status: Modified

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2026-31444 in the EU Vulnerability Database. Last updated in EUVD on August 25, 2026.

View on the EU Vulnerability Database

Affected products

debian / debian linux
f5 / dos
f5 / dos
f5 / nginx gateway fabric
f5 / nginx ingress controller
f5 / nginx instance manager
f5 / nginx open source
f5 / nginx open source
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / nginx plus
f5 / waf
redhat / discovery
redhat / enterprise linux
redhat / enterprise linux
redhat / enterprise linux
redhat / hardened images
redhat / update infrastructure

Certified products that may be affected

31 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

Red Hat Enterprise Linux 8 NSS Cryptographic Module - Red Hat, Inc. - FIPS 140 5513 - active
Red Hat Enterprise Linux 8 Kernel Cryptographic API - Red Hat, LLC - FIPS 140 5461 - active
Red Hat Enterprise Linux 9 Kernel Cryptographic API - Red Hat, Inc. - FIPS 140 5445 - active
Red Hat Enterprise Linux 9 libgcrypt - Red Hat, Inc. - FIPS 140 5366 - active
Red Hat Enterprise Linux 8 Kernel Cryptographic API - Red Hat, Inc. - FIPS 140 5089 - active

See all 31 in the Security Certifications Explorer.

References

http://www.openwall.com/lists/oss-security/2026/05/22/14(Mailing List)
https://access.redhat.com/errata/RHSA-2026:20351(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:28212(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:28921(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:28973(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:29151(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:29874(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:33313(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:44481(Third Party Advisory)
https://access.redhat.com/errata/RHSA-2026:58981
https://access.redhat.com/security/cve/CVE-2026-9256(Third Party Advisory)
https://bugzilla.redhat.com/show_bug.cgi?id=2480746(Issue Tracking, Third Party Advisory)
https://lists.debian.org/debian-lts-announce/2026/06/msg00023.html(Mailing List, Third Party Advisory)
https://my.f5.com/manage/s/article/K000161377(Mitigation, Vendor Advisory)
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-9256.json(Third Party Advisory)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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