CVE-2023-36135: User enumeration is found in in PHPJabbers Class Scheduling System v1.0

This month

HIGH 7.5REMOTEDOWNGRADE

CVE-2023-36135 is a high-severity flaw (CVSS 7.5) affecting class scheduling system. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

User enumeration is found in in PHPJabbers Class Scheduling System v1.0. This issue occurs during password recovery, where a difference in messages could allow an attacker to determine if the user is valid or not, enabling a brute force attack with valid users.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Published	2023-08-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: phpjabbers

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-08-04 00:15 UTCPublished CVE record published
2026-06-17 06:05 UTCUpdated Record last modified

phpjabbers class scheduling system DOWNGRADE

Affected: 1.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0

1. Check installed version

apt-cache policy class-scheduling-system || rpm -q class-scheduling-system || class-scheduling-system --version

2. No fixed release: DOWNGRADE to a release before 1.0 (Debian / Ubuntu)

apt-cache madison class-scheduling-system sudo apt install class-scheduling-system=<VERSION_BEFORE_1.0> sudo apt-mark hold class-scheduling-system

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list class-scheduling-system sudo dnf downgrade class-scheduling-system-<VERSION_BEFORE_1.0> sudo dnf versionlock add class-scheduling-system

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2023-36135?

class scheduling system: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-36135 being exploited?

CVE-2023-36135 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2023-36135 affect?

CVE-2023-36135 affects class scheduling system. Severity is high (CVSS 7.5). User enumeration is found in in PHPJabbers Class Scheduling System v1.0. This issue occurs during password recovery, where a difference in messages could allow an attacker to determine if the user is valid or not, enabling a brute force att

How urgent is CVE-2023-36135?

Priority 43/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2023-36137 MEDIUM 6.1 DOWNGRADE There is a Cross Site Scripting (XSS) vulnerability in the "theme" parameter of preview.php in PHPJabbers Clas
CVE-2023-36136 MEDIUM 6.5 DOWNGRADE PHPJabbers Class Scheduling System 1.0 lacks encryption on the password when editing a user account (update us
CVE-2023-36134 CRITICAL 9.8 DOWNGRADE In PHP Jabbers Class Scheduling System 1.0, lack of verification when changing an email address and/or passwor
CVE-2023-2826 LOW 3.5 DOWNGRADE A vulnerability has been found in SourceCodester Class Scheduling System 1.0 and classified as problematic
CVE-2023-2823 MEDIUM 6.3 DOWNGRADE A vulnerability was found in SourceCodester Class Scheduling System 1.0

References

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