Security Bulletin
Summary
gRPC is used by DataStage on Cloud Pak for Data as part of service communication.
Vulnerability Details
CVEID: CVE-2023-33953
DESCRIPTION: gRPC contains a vulnerability that allows hpack table accounting errors could lead to unwanted disconnects between clients and servers in exceptional cases/ Three vectors were found that allow the following DOS attacks:
- Unbounded memory buffering in the HPACK parser
- Unbounded CPU consumption in the HPACK parser
The unbounded CPU consumption is down to a copy that occurred per-input-block in the parser, and because that could be unbounded due to the memory copy bug we end up with an O(n^2) parsing loop, with n selected by the client.
The unbounded memory buffering bugs:
- The header size limit check was behind the string reading code, so we needed to first buffer up to a 4 gigabyte string before rejecting it as longer than 8 or 16kb.
- HPACK varints have an encoding quirk whereby an infinite number of 0’s can be added at the start of an integer. gRPC’s hpack parser needed to read all of them before concluding a parse.
- gRPC’s metadata overflow check was performed per frame, so that the following sequence of frames could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION: containing a: 2 CONTINUATION: containing a: 3 etc…
CWE: CWE-789: Memory Allocation with Excessive Size Value
CVSS Source: IBM X-Force
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| DataStage on Cloud Pak for Data | 5.2 |
Remediation/Fixes
IBM strongly recommends addressing the vulnerability now by upgrading to the latest 5.2 patch.
| Product(s) | Version(s) number and/or range | Remediation/Fix/Instructions |
| DataStage on Cloud Pak for Data | 5.2 | Upgrade to the latest 5.2 patch by following these instructions. |
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
23 Jul 2025: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
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Document Location
Worldwide
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Document Information
Modified date:
23 July 2025
UID
ibm17240409