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Pre-Authentication Remote Code Execution via `jato.clientSession` Deserialization in OpenAM

Not in CISA KEVPublic exploit codeCVE-2026-33439CWE-502

Not confirmed exploited. 1 of 8 rule sources name it. Our CRS test: not blocked. 1 public exploit repo.

Edge rules
1/8
Our test
Not blocked
CVSS
9.3
EPSS
9.3% Top 5%
Posts, 14d
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Published
2026-04-07
Open Access Management (OpenAM) is an access management solution. Prior to 16.0.6, OpenIdentityPlatform OpenAM is vulnerable to pre-authentication Remote Code Execution (RCE) via unsafe Java deserialization of the jato.clientSession HTTP… More

Open Access Management (OpenAM) is an access management solution. Prior to 16.0.6, OpenIdentityPlatform OpenAM is vulnerable to pre-authentication Remote Code Execution (RCE) via unsafe Java deserialization of the jato.clientSession HTTP parameter. This bypasses the WhitelistObjectInputStream mitigation that was applied to the jato.pageSession parameter after CVE-2021-35464. An unauthenticated attacker can achieve arbitrary command execution on the server by sending a crafted serialized Java object as the jato.clientSession GET/POST parameter to any JATO ViewBean endpoint whose JSP contains <jato:form> tags (e.g., the Password Reset pages). This vulnerability is fixed in 16.0.6.

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AI · answers from this page
Ask about CVE-2026-33439: who's covered, what to patch first, how vendors compare. I cite sources and won't help with attacks.

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Severity, decoded

CVSS 4.0
Critical · 9.3 / 10

Exploitable over the network, with no privileges and no user interaction, leading to full loss of confidentiality, integrity and availability.

Over the internetNo login neededNo user actionWorks reliablyFull compromise
How the score is built11 metrics
  • Attack vectorAn attacker can reach it over the internet; no access to your network needed.
    Network
  • Attack complexityNo built-in defences have to be bypassed; the attack works reliably.
    Low
  • Attack requirementsThe attack works without any special deployment or timing conditions.
    None
  • Privileges requiredNo account or login is needed.
    None
  • User interactionNo one has to click or open anything; the attack works on its own.
    None
  • Confidentiality impact (vulnerable system)An attacker can read all data the affected component holds, or the most sensitive parts of it.
    High
  • Integrity impact (vulnerable system)An attacker can change any data or files the affected component protects.
    High
  • Availability impact (vulnerable system)An attacker can take the component down completely or keep it from serving anyone.
    High
  • Confidentiality impact (other systems)Other systems' data is not exposed.
    None
  • Integrity impact (other systems)Other systems' data cannot be changed.
    None
  • Availability impact (other systems)Other systems keep working normally.
    None
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CISA's assessmentSSVC, from the CVE record
ExploitationNone

CISA has seen no public exploit and no attacks.

AutomatableYes

Attackers can script the attack end to end and hit many targets at once.

Technical impactTotal

A successful attack gives full control over the affected software or all of its data.

Public exploits

2 found
0 Metasploit0 Exploit-DB1 Scanner template1 GitHub PoCs

Links are to third-party code: never run it outside an isolated lab.

Timeline

  1. 2026-04-07
    CVE published
    CVE List
  2. 2026-09-16
    F5 ships a rule
    OpenAM Unauthenticated Remote Code Execution
  3. 2026-11-02
    First public exploit repository
    stapat1245/CVE-2026-33439_poc: Proof of Concept for CVE-2026-33439 RCE in OpenAM
  4. 2026-11-02
    First social mention we saw
  5. 2026-11-02
    Our test: OWASP Core Rule Set let it through
    paranoia level 1, anomaly threshold 5, default CRS settings
  6. 2026-11-02
    Our test: OWASP Core Rule Set let it through
    paranoia level 2, anomaly threshold 5, default CRS settings

Social

2026-10-20: 0 posts2026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 1 posts

Exploit repos · unvetted, don't run

  • stapat1245·

    stapat1245/CVE-2026-33439_poc: Proof of Concept for CVE-2026-33439 RCE in OpenAM

    ★ 1View on GitHub

Vendor statements

Quoted
CloudflareWAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Each row gives the rule ID and its default action. The feed starts in January 2025, so older rules are missing.

AWSAWS WAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. AWS often describes a vulnerability without naming its CVE (for example "Log4j"). We count only entries that name the CVE, so AWS coverage is understated.

Microsoft AzureFront Door and Application Gateway WAF (DRS)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. The rule tables name CVEs but carry no dates, so Azure is left out of every time-to-rule figure.

Google CloudCloud Armor preconfigured WAF rulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Google names few CVEs: the release notes start in May 2024 and the rules reference lists CVEs without dates. Its cve-canary rules are opt-in.

FastlyNext-Gen WAF virtual patchesBefore feed history

The CVE predates the oldest entry in this vendor's public feed, so a rule may exist that we cannot see.

F5Attack signatures (Distributed Cloud WAF)1 quoteRule published

First rule 2026-09-16, 162 days after the CVE was published.

2026-09-16New rule200204093Source
Added: signature 200204093 "OpenAM Unauthenticated Remote Code Execution" (Server Side Code Injection, risk High), systems: Other Web Server. References: CVE-2026-33439.
AkamaiApp & API Protector (Adaptive Security Engine)No public source

This vendor publishes no machine-readable rule changelog we can check.

OWASP CRSCore Rule Set (open source, used inside many WAFs)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. CRS rarely names CVEs: it relies on generic detections. Our own lab measures what it actually blocks.