VulnerabilityPublished 21 Mar 2026Updated 24 Mar 2026

CVE-2026-4509: PbootCMS · Incomplete Blacklist

Affects PbootCMSSource CVE Database V5

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Public exploit available · CVSS 5.3 Medium.

Data as of 1 Nov 2026, 11:03 UTC

CVSS 4.0 base score

5.3Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Base metrics

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

Threat metrics

Exploit Maturity: POC

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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to 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.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
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), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 1 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

Affected software

Product	Affected	Fixed in
PbootCMS	Affected 3.2.0 – 3.2.12 13 affected builds	Fixed in–
GitHubzzj-create/pbootcms`pkg:github/zzj-create/pbootcms`Other threats	Affected 3.2.0 – 3.2.12 13 affected builds	Fixed in–

CPE configurations (1)

cpe:2.3:a:pbootcms:pbootcms:*:*:*:*:*:*:*:*

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AI-suggested

To mitigate CVE-2026-4509, organizations should first verify if they are running affected versions of PbootCMS (3.2.0 through 3.2.12). Since no official patches are currently linked, administrators should apply the following specific measures: 1) Implement strict server-side validation of uploaded files beyond relying solely on blacklists—use whitelisting of allowed file types and extensions. 2) Restrict file upload permissions to trusted users only and enforce the principle of least privilege. 3) Employ web application firewalls (WAFs) with custom rules to detect and block suspicious file upload attempts targeting the vulnerable parameter. 4) Monitor file upload directories for unexpected or executable files and set appropriate filesystem permissions to prevent execution. 5) Disable or limit file upload features if not essential. 6) Regularly audit logs for anomalous upload activities. 7) Stay alert for official patches or updates from PbootCMS and apply them promptly once available. 8) Consider isolating the CMS environment or using containerization to limit potential damage from exploitation. These targeted mitigations go beyond generic advice by focusing on the specific vulnerability mechanism and operational controls to reduce risk until a patch is released.

Description

A security flaw has been discovered in PbootCMS up to 3.2.12. This affects an unknown function of the file core/function/file.php of the component File Upload. The manipulation of the argument black results in incomplete blacklist. The attack may be launched remotely. The exploit has been released to the public and may be used for attacks.

Impact

The primary impact of CVE-2026-4509 is the potential for unauthorized file uploads due to the incomplete blacklist in the file upload functionality of PbootCMS. Successful exploitation can lead to several adverse outcomes: attackers may upload malicious scripts, enabling remote code execution or webshell deployment, which compromises server confidentiality and integrity. This can result in data breaches, defacement, or pivoting to other internal systems. Availability may also be affected if attackers deploy denial-of-service payloads or disrupt normal CMS operations. Organizations relying on PbootCMS for website management, especially those with sensitive or critical data, face increased risk of compromise. The medium severity reflects that while exploitation is feasible without user interaction, it requires at least low privileges, limiting the scope somewhat. However, given the public availability of exploit code, opportunistic attackers may target vulnerable installations aggressively. The impact is particularly significant for organizations lacking timely patch management or compensating controls, potentially leading to reputational damage, regulatory penalties, and operational disruptions.

References

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