In recent times, VMware Tools has been discovered to contain a security vulnerability identified as CVE-2023-34058. This vulnerability is a SAML token signature bypass, allowing a malicious actor with Guest Operation Privileges in a target virtual machine (VM) to potentially escalate their privileges if that target VM has been assigned a more privileged Guest Alias. This blog post will outline the exploit details, provide code snippets, and link to original references to help understand the issue and its implications.

Exploit Details

CVE-2023-34058 revolves around the abuse of a SAML token signature bypass and consequently, the possibility of privilege escalation. The exploit occurs when a malicious actor gains Guest Operation Privileges (https://docs.vmware.com/en/VMware-vSphere/8./vsphere-security/GUID-6A952214-E5E-4CCF-9D2A-90948FF643EC.html) within a target VM, and that VM has been assigned a more privileged Guest Alias (https://vdc-download.vmware.com/vmwb-repository/dcr-public/d1902be-d479-46bf-8ac9-ceee31e8ec/07ce8dbd-db48-4261-9b8f-c6d3ad8ba472/vim.vm.guest.AliasManager.html).

In simple terms, a malicious actor can exploit this vulnerability to acquire higher privileges within the target VM, enabling them to perform unauthorized actions and potentially compromise the system. The primary concern with this vulnerability is that an attacker can elevate their privileges, leading to unauthorized access and control over critical resources within the VM environment.

Code Snippet

The following code snippet provides an example of how the SAML token signature bypass vulnerability CVE-2023-34058 can potentially be exploited:

#Load VMware Tools PublicKey
with open("vmware_public_key.pem", "rb") as f:
    vmware_public_key = f.read()

# Original SAML token containing signed data (issued to the attacker)
saml_token = "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJhdZ...kZBGahQ2s"

# Malicious actor modifies the SAML token data to elevate privileges
elevated_privileges_data = "Fake_guest_alias_with_more_privileges"

#Invalid signature is appended
saml_elevated_token = f"{elevated_privileges_data}-{saml_token.split('-')[1]}"

# Verify the original SAML token signature (should be valid)
isValidOriginalToken = verify_signature(vmware_public_key, saml_token)

# Verify the tampered SAML token (should be invalid)
isValidElevatedToken = verify_signature(vmware_public_key, saml_elevated_token)

if not isValidElevatedToken:
    print("Signature bypass vulnerability exists: CVE-2023-34058.")

In this code snippet, an attacker with knowledge of the VMware Tools public key can modify SAML token data to falsely elevate their privileges and bypass the original token's signature. If the signature on the tampered SAML token remains valid, there is a high risk of the vulnerability (CVE-2023-34058) being exploited for privilege escalation.

Original References

For more information on CVE-2023-34058 and the related VMware Tools vulnerabilities, refer to the following original resources:

- VMware Security Advisory VMSA-2023-0005 (https://www.vmware.com/security/advisories/VMSA-2023-0005.html)
- VMware vSphere Guest OS Security Guide (https://docs.vmware.com/en/VMware-vSphere/8./vsphere-security/GUID-6A952214-E5E-4CCF-9D2A-90948FF643EC.html)
- VMware Tools Guest Alias Documentation (https://vdc-download.vmware.com/vmwb-repository/dcr-public/d1902be-d479-46bf-8ac9-ceee31e8ec/07ce8dbd-db48-4261-9b8f-c6d3ad8ba472/vim.vm.guest.AliasManager.html)

Conclusion

CVE-2023-34058 is a critical vulnerability that poses a significant risk to VMware Tools users. The vulnerability allows malicious actors to exploit a SAML token signature bypass and escalate their privileges within a target VM environment. VMware has released patches and security advisories addressing this issue; it is highly recommended that users employ the necessary updates and remain vigilant to the potential ramifications of this vulnerability.

Timeline

Published on: 10/27/2023 05:15:38 UTC
Last modified on: 11/17/2023 05:15:12 UTC