CVE-2026-78187Public exploitNetwork attack vector

Script execution via unencoded lang cookie

Published Aug 24, 2026 · Updated Aug 24, 2026

Reflected XSS in Piwigo 16.3.0 public authentication pages allows remote attackers to execute script via a malicious lang cookie. The pages pass an invalid lang cookie to fatal_error(), which inserts the message into HTML without output encoding. Exploitation requires control of a cookie sent by the victim browser; script then runs in the affected site's origin.

CVSS severity4.7
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Piwigo 16.3.0 public authentication pages allows remote attackers to execute script via a malicious lang cookie. The pages pass an invalid lang cookie to fatal_error(), which inserts the message into HTML without output encoding. Exploitation requires control of a cookie sent by the victim browser; script then runs in the affected site's origin.

The record

CVE
CVE-2026-78187
Published
Aug 24, 2026
Updated
Aug 24, 2026
Vendor
Piwigo
Product
Piwigo
Classifications
CWE-94, CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 24, 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=16.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Piwigo · Piwigoversion=16.3.0

Published CVSS scores

4.7Piwigo GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N
2.3VulDB CNACVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
2.6VulDB CNAAV:N/AC:H/Au:N/C:N/I:P/A:N/E:POC/RL:OF/RC:C
3.1VulDB CNACVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C
3.1VulDB CNACVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-94Code Injection
CWE-79Cross Site Scripting
T1203Exploitation for Client Execution

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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