VulnerabilityPublished 11 Nov 2026

CVE-2026-126663: Contao · Incorrect Behavior Order: Validate Before Canonicalize

Affects ContaoSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium · fixed in 6.0.6 : update Contao when convenient.

Data as of 11 Nov 2026, 12:48 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (VulnCheck)	CVSS 4.0	5.3
CNA (VulnCheck)	CVSS 3.1	4.3

Patch: Available – fixed in 6.0.6, 5.7.17, 5.3.54

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 11 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Contao to 6.0.6, 5.7.17 or 5.3.54.

Affected software

Product	Affected	Fixed in
ContaoContao	Affected >=6.0.0-RC1 <6.0.6	Fixed in 6.0.6
ContaoContao	Affected >=5.4.0-RC1 <5.7.17	Fixed in 5.7.17
ContaoContao	Affected >=4.0.0 <5.3.54	Fixed in 5.3.54
PackagistContao`pkg:composer/Contao`Other threats	Affected >=4.0.0 <5.3.54 >=5.4.0-RC1 <5.7.17 >=6.0.0-RC1 <6.0.6	Fixed in 5.3.54 5.7.17 6.0.6

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Fixed versions are available: 5.3.54, 5.7.17, and 6.0.6. Users should upgrade to these or later versions to remediate the vulnerability. No other mitigation or temporary workaround is indicated by the vendor advisory.

Description

CVE-2026-126663 is a path traversal vulnerability in Contao versions 4.0.0 before 5.3.54, 5.4.0 before 5.7.17, and 6.0.0 before 6.0.6. It allows content editors to read image files anywhere on the filesystem via the {{image::}} insert tag by exploiting incorrect validation order of paths. Attackers can use percent-encoded sequences to bypass the Validator::isInsecurePath() check, causing the frontend to serve files outside the intended directory.

Impact

An attacker with content editor privileges can read arbitrary image files on the server filesystem outside the intended files directory. This could lead to unauthorized disclosure of sensitive files if such files are accessible as images. The CVSS 4.0 base score is 5.3 (medium severity), reflecting network attack vector, low complexity, no privileges required beyond content editor, and no user interaction needed.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 11 Nov 2026, 12:48 UTC

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