# CVE-2025-49601: Mbed TLS out-of-bounds read in mbedtls_lms_import_public_key

Source: https://junglewise.ai/threats/cve-2025-49601-mbed-tls-out-of-bounds-read-in-mbedtls-lms-import-public-key  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-07-04. Updated: 2026-06-05  
License: CC BY 4.0 with a link back

CVE-2025-49601 · Severity: medium · CVSS 4.8 · Published 2025-07-04

Mbed TLS is a widely used security library that provides encryption and secure communication for embedded devices. A flaw in how it handles certain digital signature keys could allow an attacker to cause a system crash or potentially view a very small amount of internal memory. This could lead to a temporary service outage for the affected device, though it does not allow for full system takeover.

Technologies: [Arm Mbed Tls](https://junglewise.ai/threats/technologies/mbed-tls). Vendors: [Arm](https://junglewise.ai/threats/vendors/arm).

## Quick answers

**Is CVE-2025-49601 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-49601 being exploited in the wild.

**How severe is CVE-2025-49601?** Medium severity, with a CVSS score of 4.8, published 4 July 2025.

**Which products and versions are affected?** Arm Mbed Tls 3.3.0 to 3.6.3.

**Is there a fix for CVE-2025-49601?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2025-49601 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2025-49601?** Check whether you run Arm Mbed Tls at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds read (CWE-125) exists in the mbedtls_lms_import_public_key() function. The root cause is a failure to validate that the input buffer is at least 4 bytes long before attempting to read a 32-bit type indicator field. An attacker can exploit this by providing a truncated LMS public key buffer (fewer than 4 bytes). This results in a buffer overread of up to 4 bytes, which can lead to undefined behavior, typically manifesting as a crash (DoS) or the leakage of whether adjacent memory matches specific fixed values. The vulnerability is present in Mbed TLS versions 3.3.0 through 3.6.3 and is fixed in version 3.6.4.

## Affected products

- Arm Mbed TLS 3.3.0 to 3.6.3
- TrustedFirmware Mbed TLS 3.3.0 to 3.6.3

## Timeline

- 2025-06-30: advisory: Vendor security advisory released
- 2025-07-04: disclosed: CVE published

## References

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

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