CyberSecBulletin
CVE-2022-35507NVD status: Modified

Proxmox Mail Gateway: Improper Neutralization of Special Elements in Output Used by a Downstream Component

Published Updated By the CyberSecBulletin desk

CVE-2022-35507 is a high-severity improper neutralization of special elements in output used by a downstream component vulnerability in Proxmox Mail Gateway from Proxmox, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. There is no confirmed exploitation so far. EPSS estimates a 1.51% chance of exploitation within 30 days, higher than 75% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Pve HTTP Server to 4.1-3 or a later version.
  2. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  3. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
ProxmoxProxmox Mail GatewayNot specified in the recordNot stated
ProxmoxPve HTTP Serverbefore 4.1-34.1-3
ProxmoxVirtual EnvironmentNot specified in the recordNot stated

Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
LowLimited modification of data is possible.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.1HighNVD
CVSS 3.14.3MediumCISA (ADP)

Official description

A response-header CRLF injection vulnerability in the Proxmox Virtual Environment (PVE) and Proxmox Mail Gateway (PMG) web interface allows a remote attacker to set cookies for a victim's browser that are longer than the server expects, causing a client-side DoS. This affects Chromium-based browsers because they allow injection of response headers with %0d. This is fixed in pve-http-server 4.1-3.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements in Output Used by a Downstream Component

The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.

How developers prevent this class of flaw

  • Programming languages and supporting technologies might be chosen which are not subject to these issues.
  • Utilize an appropriate mix of allowlist and denylist parsing to filter control-plane syntax from all input.

More Improper Neutralization of Special Elements in Output Used by a Downstream Component vulnerabilities (CWE-74)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Other vulnerabilities in Proxmox Mail Gateway

All Proxmox Mail Gateway vulnerabilities

Recent Improper Neutralization of Special Elements in Output Used by a Downstream Component vulnerabilities

Spotted an error? Tell us.