CVE-2026-91768: IPv6 ACL bypass in FastCGI listen.allowed_clients due to partial address comparison (memcmp 12 bytes)
Noroxi assessment
Priority: Monitor (action score 26/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.37% (FIRST EPSS).
- Someone on the same network segment can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: PHP Group PHP 8.2.34, 8.3.35, 8.4.26; azl3 php 8.3.33-1 on Azure Linux 3.0 8.3.35-1.
Low priority for now. Upgrade to PHP Group PHP 8.2.34, 8.3.35, 8.4.26; azl3 php 8.3.33-1 on Azure Linux 3.0 8.3.35-1 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
The IPv6 branch of the FastCGI client access check compares only the first 12 bytes of a 16-byte IPv6 address, so listen.allowed_clients matches on a /96 prefix instead of the exact address. An attacker who can source an address sharing the first 96 bits with an allowed one passes the check and reaches the FastCGI endpoint.
- Published
- Sep 25, 2026
- Updated
- Oct 27, 2026
- EPSS
- 0.3% · 31th percentile
- CWE
- CWE-1023
Report tools
Action score
26
Monitor
Low priority for now.
- CVSS
- 26 / 40 · 6.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · php
- 6.5
- NVD has not scored this yet; the score shown is the CNA’s.
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
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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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.
We use this product, ask for helpAffected 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.
| Vendor | Product | CPE |
|---|---|---|
| php | php | cpe:2.3:a:php:php |
Using php? Add it to your stack and be the first to know about CVEs like this one. (PHP)
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- php php8.2.0 and later · before 8.2.34
- php php8.3.0 and later · before 8.3.35
- php php8.4.0 and later · before 8.4.26
- php php8.5.0 and later · before 8.5.11
Versions reported by the vendor
Affected version ranges reported by the assigning authority (php). Independent of NVD's CPE analysis and usually ahead of it.
PHP Group PHP
- 8.2.* and later · before 8.2.34affected · semver
- 8.3.* and later · before 8.3.35affected · semver
- 8.4.* and later · before 8.4.26affected · semver
- 8.5.* and later · before 8.5.11affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | apcu-panel | before 5.1.18-1.module_el8.6.0+2750+78feabcb | 5.1.18-1.module_el8.6.0+2750+78feabcb |
| AlmaLinux:8 | libzip | before 1.6.1-1.module_el8.10.0+3935+28808425 | 1.6.1-1.module_el8.10.0+3935+28808425 |
| AlmaLinux:8 | libzip | before 1.6.1-1.module_el8.6.0+3239+bedf0508 | 1.6.1-1.module_el8.6.0+3239+bedf0508 |
| AlmaLinux:8 | libzip | before 1.6.1-1.module_el8.6.0+2750+78feabcb | 1.6.1-1.module_el8.6.0+2750+78feabcb |
| AlmaLinux:8 | libzip-devel | before 1.6.1-1.module_el8.6.0+2750+78feabcb | 1.6.1-1.module_el8.6.0+2750+78feabcb |
| AlmaLinux:8 | libzip-devel | before 1.6.1-1.module_el8.10.0+3935+28808425 | 1.6.1-1.module_el8.10.0+3935+28808425 |
| AlmaLinux:8 | libzip-devel | before 1.6.1-1.module_el8.6.0+3239+bedf0508 | 1.6.1-1.module_el8.6.0+3239+bedf0508 |
| AlmaLinux:8 | libzip-tools | before 1.6.1-1.module_el8.6.0+3239+bedf0508 | 1.6.1-1.module_el8.6.0+3239+bedf0508 |
| AlmaLinux:8 | libzip-tools | before 1.6.1-1.module_el8.10.0+3935+28808425 | 1.6.1-1.module_el8.10.0+3935+28808425 |
| AlmaLinux:8 | php | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-bcmath | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-cli | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-common | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-dba | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-dbg | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-devel | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-embedded | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-enchant | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-ffi | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-fpm | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-gd | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-gmp | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-intl | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
| AlmaLinux:8 | php-json | before 7.4.33-8.module_el8.10.0+4321+cf5fd4bb | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb |
+96
Same product
php: all recordsOther highest-scoring records for the same primary product.
- CVE-2024-4577Argument Injection in PHP-CGIKEV99Now
- CVE-2019-11043Underflow in PHP-FPM can lead to RCEKEV99Now
- CVE-2012-1823sapi/cgi/cgi_main.c in PHP before 5.3.12 and 5.4.x before 5.4.2, when configured as a CGI script (aka php-cgi), does not properly handle queKEV99Now
Published before and after this one in the same product
- ← EarlierCVE-2026-91767Sep 25, 2026 · Heap-buffer-overflow in php_openssl_matches_wildcard_name on crafted server cert wildcard CN26Monitor
- ← EarlierCVE-2026-91769Sep 25, 2026 · TLS Hostname Verification Falls Back to CN After SAN Mismatch17Monitor
- Later →CVE-2026-92842Sep 25, 2026 · OOB read / info leak in convert.* stream filters when line-break-chars contains NUL23Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| PHP Group PHP | 8.2.34 | Vendor (CNA) |
| PHP Group PHP | 8.3.35 | Vendor (CNA) |
| PHP Group PHP | 8.4.26 | Vendor (CNA) |
| PHP Group PHP | 8.5.11 | Vendor (CNA) |
| azl3 php 8.3.33-1 on Azure Linux 3.0 | 8.3.35-1 · Release Notes | Microsoft (MSRC) |
| almalinux:apcu-panel | 5.1.18-1.module_el8.6.0+2750+78feabcb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:libzip | 1.6.1-1.module_el8.6.0+2750+78feabcb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:libzip-devel | 1.6.1-1.module_el8.10.0+3935+28808425 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:libzip-tools | 1.6.1-1.module_el8.10.0+3935+28808425 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php-bcmath | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php-cli | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php-common | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php-dba | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php-dbg | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php-devel | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:php-embedded | 7.4.33-8.module_el8.10.0+4321+cf5fd4bb · AlmaLinux:8 | Package registry (OSV) |
| alpine:php82 | 8.2.35-r0 · Alpine:v3.22 | Package registry (OSV) |
| alpine:php83 | 8.3.36-r0 · Alpine:v3.22 | Package registry (OSV) |
| alpine:php84 | 8.4.27-r0 · Alpine:v3.22 | Package registry (OSV) |
| alpine:php85 | 8.5.12-r0 · Alpine:v3.23 | Package registry (OSV) |
| debian:php8.2 | 8.2.34-1~deb12u1 · Debian:12 | Package registry (OSV) |
| debian:php8.4 | 8.4.26-1~deb13u1 · Debian:13 | Package registry (OSV) |
| opensuse:apache2-mod_php8 | 8.4.26-160000.1.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:php8 | 8.5.11-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| opensuse:php8-embed | 8.4.26-160000.1.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:php8-fastcgi | 8.4.26-160000.1.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:php8-fpm | 8.4.26-160000.1.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:php8-test | 8.4.26-160000.1.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| red hat:php | 0:8.5.11-2.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
+35
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
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.
No dated events beyond publication.
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.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- @OSTIF-Derek (GitHub)reporter
- @l8BL (GitHub)reporter
- Ilia Alshanetskyreporter
- Alexandre Dauboisremediation developer
- Arnaud Le Blancremediation reviewer
- Jakub Zelenkaremediation reviewer
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
- Someone on the same network segment can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- none
- Availability
- none
- Attack vector
- Adjacent
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- None
- Availability impact
- None
Weakness class (CWE)
CWE-1023 · Incomplete Comparison with Missing FactorsCVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
- SSVC exploitation— → none
For records you follow, these changes also arrive as notifications. →
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.