CVE-2025-52497VulnerabilityPublished 4 Jul 2025Updated 3 Nov 2025

CVE-2025-52497: Mbed mbedtls · Off-by-one Error

Affects Mbed mbedtlsSource CVE Database V5

Not known to be exploited · CVSS 4.8 Medium : upgrade to 3.6.4 when convenient.

Data as of 26 Oct 2026, 06:15 UTC

CVSS 3.1 base score

4.8Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 26% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.6.4

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: Low

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
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: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to 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 2026-10-25.

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

Upgrade mbed-tls/mbedtls to 3.6.4.

Affected software

Product	Affected	Fixed in
GitHubmbed-tls/mbedtls`pkg:github/mbed-tls/mbedtls`Other threats	Affected <3.6.4	Fixed in 3.6.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately plan to upgrade Mbed TLS to version 3.6.4 or later once available, as this version addresses the off-by-one buffer underflow. Until patches are deployed, organizations should implement strict input validation and sanitization for PEM files, rejecting untrusted or malformed certificate data before parsing. Network-level controls such as firewall rules and intrusion detection systems should monitor and restrict access to services that accept PEM input from untrusted sources. Employ runtime protections like memory safety tools or address sanitizers during development and testing phases to detect similar memory corruption issues early. For embedded and IoT devices where patching is delayed or difficult, consider isolating affected devices from critical networks and applying compensating controls such as limiting certificate update mechanisms. Regularly audit device firmware and software versions to identify vulnerable instances of Mbed TLS. Additionally, maintain vigilant monitoring for anomalous application crashes or unusual certificate parsing errors that could indicate exploitation attempts.

Description

Mbed TLS before 3.6.4 has a PEM parsing one-byte heap-based buffer underflow, in mbedtls_pem_read_buffer and two mbedtls_pk_parse functions, via untrusted PEM input.

Impact

For European organizations, the vulnerability poses a risk primarily to embedded and IoT devices that utilize Mbed TLS for secure communications and certificate handling. Successful exploitation could lead to denial of service conditions via application crashes or limited information leakage, potentially exposing sensitive cryptographic material or causing service disruptions. This could impact critical infrastructure sectors such as manufacturing, automotive, telecommunications, and healthcare, where embedded devices are prevalent. The medium severity and high attack complexity reduce the likelihood of widespread exploitation, but targeted attacks against high-value assets remain a concern. The confidentiality impact, although low, is significant in environments where cryptographic key material is highly sensitive. Availability impacts could disrupt services relying on affected devices, leading to operational downtime. Given the increasing deployment of IoT and embedded systems across Europe, especially in industrial and smart city applications, the vulnerability could have cascading effects if exploited in critical systems.

CWE-193Off-by-one Error (opens in a new tab)
Base weakness
A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
Implementation
When copying character arrays or using character manipulation methods, the correct size parameter must be used to account for the null terminator that needs to be added at the end of the array.
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2025, 01:38 UTC

WeaknessesCWE-193

Technical details

References

Community reviews

Related threats