VulnerabilityPublished 4 Jul 2025Updated 8 Jul 2025

CVE-2025-49600: Mbed mbedtls · Missing Cryptographic Step

Affects Mbed mbedtlsSource CVE Database V5

Not known to be exploited · CVSS 4.9 Medium.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

4.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Physical
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Physical: The attack requires the attacker to physically touch or manipulate the vulnerable component. Physical interaction may be brief or persistent.
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GitHubmbed-tls/mbedtls`pkg:github/mbed-tls/mbedtls`Other threats	Affected =3.3.0	Fixed in–

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AI-suggested

European organizations should first identify all systems and devices using affected MbedTLS versions (3.3.0 up to 3.6.4) with hardware-accelerated hashing enabled. Immediate mitigation steps include: 1) Upgrading MbedTLS to version 3.6.4 or later where the vulnerability is fixed. 2) If upgrading is not immediately feasible, disabling hardware acceleration for hashing temporarily to force use of the software SHA-256 implementation, which is not vulnerable. 3) Implementing hardware fault detection and mitigation mechanisms to prevent fault injection attacks, such as monitoring for abnormal hardware behavior or using hardware with built-in fault resistance. 4) Enhancing code auditing and error checking in cryptographic verification functions to ensure all return values are validated. 5) Employing layered security controls such as code signing with multiple independent verification steps and runtime integrity checks to detect forged signatures. 6) Monitoring for anomalous signature verification failures or suspicious activity that may indicate exploitation attempts. These steps go beyond generic advice by focusing on the specific fault injection vector and hardware acceleration context of this vulnerability.

Description

In MbedTLS 3.3.0 before 3.6.4, mbedtls_lms_verify may accept invalid signatures if hash computation fails and internal errors go unchecked, enabling LMS (Leighton-Micali Signature) forgery in a fault scenario. Specifically, unchecked return values in mbedtls_lms_verify allow an attacker (who can induce a hardware hash accelerator fault) to bypass LMS signature verification by reusing stale stack data, resulting in acceptance of an invalid signature. In mbedtls_lms_verify, the return values of the internal Merkle tree functions create_merkle_leaf_value and create_merkle_internal_value are not checked. These functions return an integer that indicates whether the call succeeded or not. If a failure occurs, the output buffer (Tc_candidate_root_node) may remain uninitialized, and the result of the signature verification is unpredictable. When the software implementation of SHA-256 is used, these functions will not fail. However, with hardware-accelerated hashing, an attacker could use fault injection against the accelerator to bypass verification.

Impact

For European organizations, this vulnerability poses a risk primarily to systems relying on MbedTLS for cryptographic signature verification, especially those using hardware-accelerated hashing modules. The ability to forge LMS signatures undermines the integrity of digital signatures, potentially allowing attackers to bypass authentication, validate malicious firmware or software updates, or impersonate trusted entities. This can lead to unauthorized code execution, supply chain compromise, or fraudulent transactions. Sectors such as telecommunications, critical infrastructure, IoT device manufacturers, and embedded systems developers in Europe are particularly at risk, as they often use MbedTLS in constrained environments with hardware acceleration for performance. The attack complexity is high due to the need for fault injection capabilities, which limits widespread exploitation but does not eliminate targeted attacks by sophisticated adversaries. The medium CVSS score reflects the limited attack vector and lack of confidentiality or availability impact but highlights the significant integrity risk. Organizations relying on hardware-accelerated cryptographic verification should be vigilant, as successful exploitation could undermine trust in digital signatures and cryptographic assurances.

CWE-325Missing Cryptographic Step (opens in a new tab)
Base weaknessOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product does not implement a required step in a cryptographic algorithm, resulting in weaker encryption than advertised by the algorithm.
OWASP Cheat Sheets
Cryptographic Storage (opens in a new tab)
Key Management (opens in a new tab)
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.7 (opens in a new tab)
V2.9.3 (opens in a new tab)
V6.2.2 (opens in a new tab)
Attack patterns
Subvert Code-signing Facilities (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/Mbed-TLS/mbedtls-docs/blob/main/security-advisories/mbedtls-security-advisory-2025-06-3.md (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Jul 2025, 21:23 UTC

WeaknessesCWE-325

Technical details

References

Community reviews

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