CVE-2024-2756Public exploitNetwork attack vector

Cookie prefix bypass via name normalization

Published Apr 29, 2024 · Updated Nov 4, 2025

Cookie parsing in The PHP Group's PHP before 8.1.28, 8.2.18, and 8.3.5 allows remote attackers to bypass protected cookie prefixes. The HTTP cookie-name parser normalizes a crafted _[Host- prefix into __Host-, causing an insecure cookie to enter $_COOKIE under a protected name. A network or same-site attacker must first set the crafted cookie in a victim's browser; an application that trusts prefix semantics then consumes attacker-controlled state as a protected cookie.

CVSS severity6.5
Medium
EPSS probability38.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cookie parsing in The PHP Group's PHP before 8.1.28, 8.2.18, and 8.3.5 allows remote attackers to bypass protected cookie prefixes. The HTTP cookie-name parser normalizes a crafted _[Host- prefix into __Host-, causing an insecure cookie to enter $_COOKIE under a protected name. A network or same-site attacker must first set the crafted cookie in a victim's browser; an application that trusts prefix semantics then consumes attacker-controlled state as a protected cookie.

The record

CVE
CVE-2024-2756
Published
Apr 29, 2024
Updated
Nov 4, 2025
Vendor
The PHP Group
Product
PHP
Classifications
CWE-20
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 29, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 4, 2025Record 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=8.1.* <8.1.28
  2. Affected versionversion=8.2.* <8.2.18
  3. Affected versionversion=8.3.* <8.3.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The PHP Group · PHPversion=8.1.* <8.1.28; version=8.2.* <8.2.18; version=8.3.* <8.3.5
The PHP Group · Archive_Tarversion=*

Published CVSS scores

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

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation

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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Your stack

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