SECURITY_THREAT_PULSE
LIVE
LAST UPDATED
FIRST SEEN
3 SOURCES ON THIS EVENT
▲ ACT NOWCVE-2021-23758 · CVSS 8.1

Ajax.NET Professional: attackers can run their own code

AFFECTSAjax.NET Professional

OFFICIAL NAME: Ajax.NET Professional Deserialization of Untrusted Data Vulnerability

WHAT IT IS · WEBSITE OR ONLINE STOREIt runs public websites, online stores or the software behind them.

DO THIS FIRSTAsk whoever runs your website or store to update it. Not sure if you use it? Send this page to your IT provider or security lead and ask.

TECHNICAL SUMMARY Ajax.NET Professional (AjaxPro) contains a deserialization of untrusted data vulnerability that could allow for remote code execution via arbitrary .NET classes. The impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.

WHY THIS VERDICT Attacks are confirmed. Ready-made attack tools are public. The exploit prediction score is 83%.

HIGHEST CONFIRMED RUNG
EXPLOITED
CISA KEV
LISTED
EXPLOIT CODE
READY TO USE
// EVIDENCE LADDER

How far has it climbed?

CONFIRMED
REPORTED
NO EVIDENCE

  1. 01 TALK

    □ NO EVIDENCE YET
    NEWEST EVIDENCE NONE YET

    No evidence yet.

    SRC: NONE YET

  2. 02 EXPOSED

    □ NOT TRACKED YET
    NO SOURCE FOR THIS STEP YET

    We have no source that counts exposed systems yet. Internet scan data needs a partnership we do not have. No evidence here does not mean nothing is exposed.

  3. 03 TRIED

    ■ CONFIRMED
    NEWEST EVIDENCE · 2 INDEPENDENT SOURCES

    Attacks that worked are confirmed (step 4), so attempts count as confirmed too.

  4. 04 EXPLOITED

    ■ CONFIRMED
    NEWEST EVIDENCE · 2 INDEPENDENT SOURCES

    Ajax.NET Professional (AjaxPro) contains a deserialization of untrusted data vulnerability that could allow for remote code execution via arbitrary .NET classes. The impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version. CISA Vulnrichment marks CVE-2021-23758 as actively exploited.

  5. 05 DAMAGE

    □ NOT TRACKED YET
    NO SOURCE FOR THIS STEP YET

    Breach notices and filings rarely name the flaw that was used, so we cannot link them to this event yet. No evidence here does not mean no harm.

// THE CLOCK

When each thing happened

  1. DISCLOSED
    CVE-2021-23758 published
  2. EXPLOIT CODE PUBLIC
    DATE UNKNOWN
  3. FIRST ATTACK REPORT
    CISA Known Exploited Vulnerabilities
  4. CISA KEV LISTING
    CISA KEV listing
  5. US FEDERAL DEADLINE
    CISA deadline for US federal agencies
Attacks were reported 1727 days after disclosure. CISA listed it 1727 days after disclosure.

THE FIX

CISA's instruction: apply the vendor's fix, or stop using the product if no fix exists. The deadline CISA set for US federal agencies, Sep 9, 2026, has passed. It is a US government deadline; use it as a guide.

// ASK YOUR TEAM

Questions to ask this week

// TIMELINE · PACIFIC TIME

How it unfolded

  1. DEC 2, 2021
    Metasploit exploit module: AjaxPro Deserialization Remote Code Execution
  2. Attack activity. DEC 3, 2021
    CISA Vulnrichment marks CVE-2021-23758 as actively exploited
  3. Attack activity. AUG 25, 2026
    Ajax.NET Professional Deserialization of Untrusted Data Vulnerability

SOURCES

  1. [1] CISA Known Exploited Vulnerabilities: Ajax.NET Professional Deserialization of Untrusted Data Vulnerability, AUG 25
  2. [2] CVE List V5 and CISA Vulnrichment: CISA Vulnrichment marks CVE-2021-23758 as actively exploited, DEC 3
  3. [3] Metasploit module metadata: Metasploit exploit module: AjaxPro Deserialization Remote Code Execution, DEC 2