VulnerabilityPublished 3 Apr 2024Updated 6 Sep 2024

CVE-2024-28755: mbedtls · Inadequate Encryption Strength

Affects mbedtlsSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 3.6.0 when convenient.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.6.0

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
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: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
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: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on 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 3 Apr 2024
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 or the CVSS exploit maturity 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 3.6.0.

Affected software

Product	Affected	Fixed in
GitHubmbed-tls/mbedtls`pkg:github/mbed-tls/mbedtls`Other threats	Affected >=3.5.0 <3.6.0	Fixed in 3.6.0

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

AI-suggested

To mitigate CVE-2024-28755, organizations should immediately upgrade all Mbed TLS deployments to version 3.6.0 or later, where the vulnerability is resolved. For environments where immediate upgrade is not feasible, implement strict network-level controls to limit exposure of TLS servers using vulnerable Mbed TLS versions to untrusted networks. Monitor TLS negotiation logs for unusual downgrade patterns or repeated failed TLS 1.3 handshakes that may indicate exploitation attempts. Employ intrusion detection systems (IDS) with signatures or heuristics tailored to detect abnormal TLS version negotiation behaviors. Review and harden TLS configuration to explicitly disable fallback to TLS 1.2 where possible, enforcing minimum TLS 1.3 usage. For embedded and IoT devices, coordinate with vendors to obtain patched firmware or software updates. Conduct thorough testing of TLS session reset functionality post-patching to ensure the maximum TLS version is correctly restored. Maintain an inventory of all systems using Mbed TLS to prioritize remediation efforts. Finally, educate security teams about this vulnerability and its indicators to improve detection and response capabilities.

Description

An issue was discovered in Mbed TLS 3.5.x before 3.6.0. When an SSL context was reset with the mbedtls_ssl_session_reset() API, the maximum TLS version to be negotiated was not restored to the configured one. An attacker was able to prevent an Mbed TLS server from establishing any TLS 1.3 connection, potentially resulting in a Denial of Service or forced version downgrade from TLS 1.3 to TLS 1.2.

Impact

The primary impact of CVE-2024-28755 is on the availability and integrity of TLS-secured communications using vulnerable versions of Mbed TLS. Organizations relying on Mbed TLS for secure server-client communications may experience denial of service conditions where TLS 1.3 connections cannot be established, potentially disrupting critical services. Additionally, the forced downgrade to TLS 1.2 reduces the security posture by exposing communications to known weaknesses in older TLS versions, increasing the risk of interception or manipulation. This can affect embedded systems, IoT devices, and applications that depend on Mbed TLS for secure communications. While confidentiality is not directly compromised, the downgrade attack vector can indirectly facilitate further attacks. The ease of exploitation without authentication or user interaction means attackers can remotely target vulnerable servers, potentially impacting large-scale deployments. The lack of known exploits in the wild currently limits immediate widespread impact, but the vulnerability represents a significant risk if weaponized. Organizations in sectors such as telecommunications, industrial control, healthcare, and consumer IoT are particularly at risk due to their reliance on embedded TLS implementations.

CWE-326Inadequate Encryption Strength (opens in a new tab)
Class weaknessOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product stores or transmits sensitive data using an encryption scheme that is theoretically sound, but is not strong enough for the level of protection required.
Architecture and Design
Use an encryption scheme that is currently considered to be strong by experts in the field.
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
V2.8.3 (opens in a new tab)
V6.2.7 (opens in a new tab)
V6.2.4 (opens in a new tab)
Attack patterns
Encryption Brute Forcing (opens in a new tab)
Brute Force (opens in a new tab)
Protocol Analysis (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Feb 2026, 10:28 UTC

WeaknessesCWE-326

Technical details

References

Community reviews

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