CVE-2025-49600

Signature forgery via unchecked hash failures

Published Jul 4, 2025 · Updated Jul 8, 2025

LMS signature verification in Mbed TLS 3.3.0 through 3.6.3 allows physically proximate attackers to make invalid signatures pass. The mbedtls_lms_verify function ignores failures from create_merkle_leaf_value and create_merkle_internal_value, leaving a prior root value on the stack. Exploitation requires fault injection against a hardware hash accelerator after a valid check and permits a changed message to reuse the valid signature; software SHA-256 is unaffected.

CVSS severity4.9
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

LMS signature verification in Mbed TLS 3.3.0 through 3.6.3 allows physically proximate attackers to make invalid signatures pass. The mbedtls_lms_verify function ignores failures from create_merkle_leaf_value and create_merkle_internal_value, leaving a prior root value on the stack. Exploitation requires fault injection against a hardware hash accelerator after a valid check and permits a changed message to reuse the valid signature; software SHA-256 is unaffected.

The record

CVE
CVE-2025-49600
Published
Jul 4, 2025
Updated
Jul 8, 2025
Vendor
TrustedFirmware.org
Product
Mbed TLS
Classifications
CWE-325
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.3.0 <3.6.4

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

TrustedFirmware.org · Mbed TLSversion=3.3.0 <3.6.4

Published CVSS scores

4.9MITRECVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-325Missing Cryptographic Step

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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