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Vulnerability Details :

CVE-2026-39963

Summary
Assigner-GitHub_M
Assigner Org ID-a0819718-46f1-4df5-94e2-005712e83aaa
Published At-14 Apr, 2026 | 23:31
Updated At-15 Apr, 2026 | 13:23
Rejected At-
Credits

Serendipity: Host Header Injection enables authentication cookie scoping to an attacker-controlled domain

Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the serendipity_setCookie() function in include/functions_config.inc.php uses $_SERVER['HTTP_HOST'] without validation as the domain parameter of setcookie(). An attacker who can influence the Host header at login time, such as via MITM, reverse proxy misconfiguration, or load balancer manipulation, can force authentication cookies including session tokens and auto-login tokens to be scoped to an attacker-controlled domain. This enables session fixation, token leakage to attacker-controlled infrastructure, and privilege escalation if an admin logs in under a poisoned Host header. This issue has been fixed in version 2.6.0.

Vendors
-
Not available
Products
-
Metrics (CVSS)
VersionBase scoreBase severityVector
Weaknesses
Attack Patterns
Solution/Workaround
References
HyperlinkResource Type
EPSS History
Score
Latest Score
-
N/A
No data available for selected date range
Percentile
Latest Percentile
-
N/A
No data available for selected date range
Stakeholder-Specific Vulnerability Categorization (SSVC)
▼Common Vulnerabilities and Exposures (CVE)
cve.org
Assigner:GitHub_M
Assigner Org ID:a0819718-46f1-4df5-94e2-005712e83aaa
Published At:14 Apr, 2026 | 23:31
Updated At:15 Apr, 2026 | 13:23
Rejected At:
▼CVE Numbering Authority (CNA)
Serendipity: Host Header Injection enables authentication cookie scoping to an attacker-controlled domain

Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the serendipity_setCookie() function in include/functions_config.inc.php uses $_SERVER['HTTP_HOST'] without validation as the domain parameter of setcookie(). An attacker who can influence the Host header at login time, such as via MITM, reverse proxy misconfiguration, or load balancer manipulation, can force authentication cookies including session tokens and auto-login tokens to be scoped to an attacker-controlled domain. This enables session fixation, token leakage to attacker-controlled infrastructure, and privilege escalation if an admin logs in under a poisoned Host header. This issue has been fixed in version 2.6.0.

Affected Products
Vendor
s9y
Product
Serendipity
Versions
Affected
  • < 2.6.0
Problem Types
TypeCWE IDDescription
CWECWE-565CWE-565: Reliance on Cookies without Validation and Integrity Checking
Type: CWE
CWE ID: CWE-565
Description: CWE-565: Reliance on Cookies without Validation and Integrity Checking
Metrics
VersionBase scoreBase severityVector
3.16.9MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N
Version: 3.1
Base score: 6.9
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf
x_refsource_CONFIRM
https://github.com/s9y/Serendipity/releases/tag/2.6.0
x_refsource_MISC
Hyperlink: https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf
Resource:
x_refsource_CONFIRM
Hyperlink: https://github.com/s9y/Serendipity/releases/tag/2.6.0
Resource:
x_refsource_MISC
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf
exploit
Hyperlink: https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf
Resource:
exploit
Information is not available yet
▼National Vulnerability Database (NVD)
nvd.nist.gov
Source:security-advisories@github.com
Published At:15 Apr, 2026 | 04:17
Updated At:23 Apr, 2026 | 13:58

Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the serendipity_setCookie() function in include/functions_config.inc.php uses $_SERVER['HTTP_HOST'] without validation as the domain parameter of setcookie(). An attacker who can influence the Host header at login time, such as via MITM, reverse proxy misconfiguration, or load balancer manipulation, can force authentication cookies including session tokens and auto-login tokens to be scoped to an attacker-controlled domain. This enables session fixation, token leakage to attacker-controlled infrastructure, and privilege escalation if an admin logs in under a poisoned Host header. This issue has been fixed in version 2.6.0.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary3.16.9MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N
Type: Secondary
Version: 3.1
Base score: 6.9
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N
CPE Matches

s9y
s9y
>>serendipity>>Versions before 2.6.0(exclusive)
cpe:2.3:a:s9y:serendipity:*:*:*:*:*:*:*:*
s9y
s9y
>>serendipity>>2.6.0
cpe:2.3:a:s9y:serendipity:2.6.0:beta1:*:*:*:*:*:*
Weaknesses
CWE IDTypeSource
CWE-565Secondarysecurity-advisories@github.com
CWE ID: CWE-565
Type: Secondary
Source: security-advisories@github.com
Evaluator Description

Evaluator Impact

Evaluator Solution

Vendor Statements

References
HyperlinkSourceResource
https://github.com/s9y/Serendipity/releases/tag/2.6.0security-advisories@github.com
Product
https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gfsecurity-advisories@github.com
Exploit
Vendor Advisory
Mitigation
https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf134c704f-9b21-4f2e-91b3-4a467353bcc0
Exploit
Vendor Advisory
Mitigation
Hyperlink: https://github.com/s9y/Serendipity/releases/tag/2.6.0
Source: security-advisories@github.com
Resource:
Product
Hyperlink: https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf
Source: security-advisories@github.com
Resource:
Exploit
Vendor Advisory
Mitigation
Hyperlink: https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Resource:
Exploit
Vendor Advisory
Mitigation

Change History

0
Information is not available yet

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