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CVE-2026-9256· NVD / CVE Program· CNA f5

NGINX ngx_http_rewrite_module vulnerability

Noroxi assessment

Priority: Monitor (action score 37/100)

  • Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 2.6% (FIRST EPSS); higher than 85.6% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: nginx (AlmaLinux:10) 2:1.26.3-6.el10_2.4; nginx-all-modules (AlmaLinux:10) 2:1.26.3-6.el10_2.4; nginx-core (AlmaLinux:10) 2:1.26.3-6.el10_2.4.

Low priority for now. Upgrade to nginx (AlmaLinux:10) 2:1.26.3-6.el10_2.4; nginx-all-modules (AlmaLinux:10) 2:1.26.3-6.el10_2.4; nginx-core (AlmaLinux:10) 2:1.26.3-6.el10_2.4 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

CriticalCVSS 9.2 · v4.0—Proof of concept Fix available
Published
May 22, 2026
Updated
Aug 25, 2026
EPSS
2.6% · 85th percentile

Report tools

JSON

Action score

37

Monitor

Low priority for now.

CVSS
36 / 40 · 9.2 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.6%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · f5
8.1
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-9256

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
f5nginx open source
f5nginx plus
f5dos
f5nginx gateway fabric
f5nginx ingress controller
f5nginx instance manager
f5waf
redhatdiscovery
redhathardened images
redhatupdate infrastructure
debiandebian linux
redhatenterprise linux

Using nginx open source? Add it to your stack and be the first to know about CVEs like this one. (Nginx)

Watch new CVEs for nginx open source

When you'll hear from us

  • when a new CVE affecting this product is published
  • when a record in your stack enters KEV or gets exploit code

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • f5 nginx open source0.1.17 and later · up to 0.9.7 inclusive
  • f5 nginx open source1.0.0 and later · before 1.30.2
  • f5 nginx open source1.31.0
  • f5 nginx plusr33 and later · before r36
  • f5 nginx plus37.0.0.1
  • f5 nginx plusr32
  • f5 nginx plusr36

Versions reported by the vendor

Affected version ranges reported by the assigning authority (f5). Independent of NVD's CPE analysis and usually ahead of it.

  • F5 NGINX Open Source

    • 1.31.0 and later · before 1.31.1affected
    • 1.30.0 and later · before 1.30.2affected
    • 0.1.17 and later · up to and including 0.9.7affected

  • F5 NGINX Plus

    • 37.0 and later · before 37.0.1.1affected
    • R36 and later · before R36 P5affected
    • R32 and later · before R32 P7affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10nginxbefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-all-modulesbefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-corebefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-filesystembefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-mod-develbefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-mod-http-image-filterbefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-mod-http-perlbefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-mod-http-xslt-filterbefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-mod-mailbefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:10nginx-mod-streambefore 2:1.26.3-6.el10_2.42:1.26.3-6.el10_2.4
AlmaLinux:8nginxbefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-all-modulesbefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-filesystembefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-mod-develbefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-mod-http-image-filterbefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-mod-http-perlbefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-mod-http-xslt-filterbefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-mod-mailbefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:8nginx-mod-streambefore 1:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.11:1.24.0-3.module_el8.10.0+4200+fea3b4c7.2.alma.1
AlmaLinux:9nginxbefore 2:1.26.3-9.module_el9.8.0+260+95b8e5ed.12:1.26.3-9.module_el9.8.0+260+95b8e5ed.1
AlmaLinux:9nginxbefore 2:1.20.1-28.el9_8.3.alma.12:1.20.1-28.el9_8.3.alma.1
AlmaLinux:9nginxbefore 1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.11:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1
AlmaLinux:9nginx-all-modulesbefore 2:1.26.3-9.module_el9.8.0+260+95b8e5ed.12:1.26.3-9.module_el9.8.0+260+95b8e5ed.1
AlmaLinux:9nginx-all-modulesbefore 2:1.20.1-28.el9_8.3.alma.12:1.20.1-28.el9_8.3.alma.1

+96

Same product

f5: all records

Other highest-scoring records for the same primary product.

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:nginx1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-all-modules1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-core1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-filesystem1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-mod-devel1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-mod-http-image-filter1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-mod-http-perl1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-mod-http-xslt-filter1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-mod-mail1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
almalinux:nginx-mod-stream1:1.24.0-7.module_el9.8.0+259+a3b861bb.2.alma.1 · AlmaLinux:9Package registry (OSV)
alpine:nginx1.26.3-r1 · Alpine:v3.21Package registry (OSV)
debian:nginx1.22.1-9+deb12u8 · Debian:12Package registry (OSV)
opensuse:nginx1.31.1-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:nginx0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-all-modules0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-core0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-core1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-core-debuginfo1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-debuginfo1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-debugsource1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-filesystem0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-filesystem1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-mod-devel0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-mod-devel1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-mod-http-geoip0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-mod-http-image-filter0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-mod-http-image-filter1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-mod-http-image-filter-debuginfo1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:nginx-mod-http-perl0:1.30.2-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nginx-mod-http-perl1:1.24.0-7.module+el9.8.0+24379+0344c460.2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+7

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Proof-of-concept repository on GitHub ×4

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:02026-05-24
Proof-of-concept repository on GitHubstars:22026-05-28
Proof-of-concept repository on GitHubstars:32026-05-28
Proof-of-concept repository on GitHubstars:12026-06-03

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+2 d
  3. TodayOct 16, 2026+147 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-122 · Heap-based Buffer Overflow

CVSS 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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (14 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records