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VulnerabilityPublished Updated

CVE-2026-91767: PHP · Heap-based Buffer Overflow

Affects PHPSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium · fixed in 8.5.11 : update PHP when convenient.

Data as of 7 Nov 2026, 23:24 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 8.5.11, 8.4.26, 8.3.35 +1
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 25 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.

What to do

Upgrade PHP to 8.5.11, 8.4.26, 8.3.35 or 8.2.34.

Affected software

ProductAffectedFixed in
PHP GroupPHPAffected
  • ≥ 8.5.*, < 8.5.11
Fixed in
  • 8.5.11
PHP GroupPHPAffected
  • ≥ 8.4.*, < 8.4.26
Fixed in
  • 8.4.26
PHP GroupPHPAffected
  • ≥ 8.3.*, < 8.3.35
Fixed in
  • 8.3.35
PHP GroupPHPAffected
  • ≥ 8.2.*, < 8.2.34
Fixed in
  • 8.2.34

AI-suggested

If you cannot patch yet, users should be cautious when connecting to untrusted TLS servers. Since verify_peer_name is enabled by default, disabling it is not recommended without understanding the security implications.

Description

A heap-based buffer overflow vulnerability exists in PHP's OpenSSL extension function php_openssl_matches_wildcard_name(). This occurs when a TLS server certificate presents a wildcard name whose literal characters are longer than the hostname being verified, causing an underflow in the length argument passed to memchr(). This can lead to reading memory beyond the allocated heap buffer. The vulnerability is reachable from any default PHP client stream since verify_peer_name is enabled by default.

References

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