CVE-2026-91767Public exploitNetwork attack vectorHinoki check available

TLS client crash via wildcard-length underflow

Published Sep 25, 2026 · Updated Sep 25, 2026

Heap buffer overflow in PHP 8.2 through 8.5 allows remote attackers controlling a TLS server to crash PHP clients. In ext/openssl/xp_ssl.c, php_openssl_matches_wildcard_name() subtracts the wildcard prefix and suffix lengths from a shorter hostname in size_t arithmetic, wrapping the memchr() bound to SIZE_MAX. The path is enabled by default through verify_peer_name; the attacker must control the contacted server or present a certificate trusted by the configured CA, and no heap data is returned.

CVSS severity6.5
Medium
EPSS probability0.15%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Heap buffer overflow in PHP 8.2 through 8.5 allows remote attackers controlling a TLS server to crash PHP clients. In ext/openssl/xp_ssl.c, php_openssl_matches_wildcard_name() subtracts the wildcard prefix and suffix lengths from a shorter hostname in size_t arithmetic, wrapping the memchr() bound to SIZE_MAX. The path is enabled by default through verify_peer_name; the attacker must control the contacted server or present a certificate trusted by the configured CA, and no heap data is returned.

The record

CVE
CVE-2026-91767
Published
Sep 25, 2026
Updated
Sep 25, 2026
Vendor
PHP Development Team
Product
PHP
Classifications
CWE-122, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.2.* <8.2.34
  2. Affected versionversion=8.3.* <8.3.35
  3. Affected versionversion=8.4.* <8.4.26
  4. Affected versionversion=8.5.* <8.5.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PHP Development Team · PHPversion=8.2.* <8.2.34; version=8.3.* <8.3.35; version=8.4.* <8.4.26; version=8.5.* <8.5.11

Published CVSS scores

6.5The PHP GroupCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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