CVE-2026-91768
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Exploit Intelligence
Moderate risk: more likely to be exploited than 45% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1023 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2021-23146 | High | 7.1 | 0.9% | - | Fix |
| CVE-2025-55333 | High | 6.1 | 0.9% | - | Fix |
| CVE-2026-81376 | High | 9.6 | 0.8% | - | Fix |
| CVE-2026-4599 | Critical | 9.1 | 0.8% | - | Fix |
| CVE-2026-7473 | Medium | 5.8 | 0.6% | KEV | - |
| CVE-2026-24255 | High | 7.5 | 0.5% | - | - |
Common questions
How do I fix CVE-2026-91768?
Upgrade php8.2 on debian 12 to 8.2.34-1~deb12u1 or later.
Is CVE-2026-91768 being actively exploited?
Not that we know of. CVE-2026-91768 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.56% is the estimated probability that it will be exploited in the next 30 days. That is higher than 45% of all scored CVEs.
How severe is CVE-2026-91768?
CVE-2026-91768 has a CVSS v3 base score of 6.5, rated moderate. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-91768 affect?
Published advisories record a fix for php8.2 (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-29.