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Netweaver AbapApplication · Sap

CVE-2021-27633

HIGH · 7.5 CVSS v3.1 Published 2021-06-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
SAP NetWeaver AS for ABAP (RFC Gateway), versions - KRNL32NUC - 7.22,7.22EXT, KRNL64NUC - 7.22,7.22EXT,7.49, KRNL64UC - 8.04,7.22,7.22EXT,7.49,7.53,7.73, KERNEL - 7.22,8.04,7.49,7.53,7.73,7.77,7.81,7.82,7.83, allows an unauthenticated attacker without specific knowledge of the system to send a specially crafted packet over a network which will trigger an internal error in the system due to improper input validation in method ThCPIC() causing the system to crash and rendering it unavailable. In this attack, no data in the system can be viewed or modified.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

SAP NetWeaver AS ABAP RFC Gateway contains an improper input validation vulnerability in the ThCPIC() method. An unauthenticated remote attacker can send a specially crafted packet over the network that triggers an internal error, causing the ABAP system to crash and become unavailable. No data exfiltration or modification is possible - this is a denial-of-service condition.

MitigationApply SAP kernel patches for the affected versions (KRNL32NUC, KRNL64NUC, KRNL64UC, KERNEL) as specified in the relevant SAP Security Note. Implement network segmentation to limit exposure to the RFC Gateway ports if patching cannot be performed immediately.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Netweaver AbapApplication
Affected:= kernel_7.22= kernel_7.49= kernel_7.53= kernel_7.73= kernel_8.04= krnl32nuc_7.22= krnl32nuc_7.22ext= krnl64nuc_7.22= krnl64nuc_7.22ext= krnl64nuc_7.49= krnl64uc_7.22= krnl64uc_7.22ext

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if SAP NetWeaver ABAP is installed
    Check for SAP processes or directories: look for /usr/sap/ directory, or run 'ps -ef | grep -i sap' to list SAP-related processes. Alternatively, check for SM51 transaction availability in the ABAP system.
    Affected if No SAP NetWeaver ABAP processes or directories are found - the system is not affected.
  2. Determine the SAP kernel version
    Run 'sapcontrol -nr <instance_number> -function GetVersionInfo' on the application server, or check the kernel executable files in /usr/sap/<SID>/SYS/exe/run/ directory for files named 'gwrd' or 'disp+work' and query their version information.
    Affected if The kernel version matches one of the affected versions: 7.22, 7.49, 7.53, 7.73, or 8.04 for kernel/krnl64uc/krnl64nuc/krnl32nuc variants.
  3. Verify the RFC Gateway process is running
    Execute 'sapcontrol -nr <instance_number> -function GetProcessList' and look for the 'gwrd' process (SAP Gateway for RFC) in the running state. Alternatively, check via SM37 transaction for process gwrd.
    Affected if The gwrd process is not running - the RFC Gateway is not active and the vulnerability cannot be exploited.
  4. Confirm network exposure of RFC Gateway ports
    Review firewall rules or run 'netstat -tlnp | grep -E "(33|36)" ' to list ports in the 3300-3399 or 3600-3699 range typically used for SAP Gateway (sapgw00, sapgw01, etc.). Check if these ports are bound to non-internal network interfaces.
    Affected if RFC Gateway ports are exposed to untrusted networks or accessible externally - the system is vulnerable to remote exploitation.

The environment is affected if it runs SAP NetWeaver ABAP with a kernel version matching 7.22, 7.49, 7.53, 7.73, or 8.04, has the RFC Gateway (gwrd) active, and has the Gateway ports exposed to network access.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply SAP kernel patches for the affected versions (KRNL32NUC, KRNL64NUC, KRNL64UC, KERNEL) as specified in the relevant SAP Security Note. Implement network segmentation to limit exposure to the RFC Gateway ports if patching cannot be performed immediately.

Fix this in Netweaver Abap Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-27633 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data