VulnerabilityPublished 3 Apr 2024Updated 18 Nov 2024

CVE-2024-28836: mbedtls

Affects mbedtlsSource CVE Database V5

Not known to be exploited · CVSS 5.4 Medium : upgrade to 3.6.0 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.4Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 35% 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:L/UI:N/S:U/C:L/I:L/A:N

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

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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: 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: None: There is no impact to availability within 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 <3.6.0	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-2024-28836, organizations should upgrade Mbed TLS to version 3.6.0 or later, where the vulnerability is fixed. If upgrading immediately is not feasible, consider the following specific measures: 1) Avoid disabling TLS 1.2 at build time if TLS 1.2 clients are expected, or ensure proper handling of ClientHello messages to prevent infinite loops. 2) Implement network-level filtering to block TLS 1.2 ClientHello messages from untrusted sources to reduce attack surface. 3) Monitor server logs for repeated TLS 1.2 handshake attempts that may indicate exploitation attempts. 4) Test TLS configurations thoroughly to confirm that disabling TLS 1.2 does not allow fallback or unintended connections. 5) For embedded or IoT devices using Mbed TLS, coordinate with vendors for firmware updates addressing this issue. 6) Employ rate limiting and DoS protection mechanisms at the network perimeter to mitigate potential impact from repeated handshake attempts. These targeted steps go beyond generic TLS hardening by addressing the specific negotiation flaw and its operational context.

Description

An issue was discovered in Mbed TLS 3.5.x before 3.6.0. When negotiating the TLS version on the server side, it can fall back to the TLS 1.2 implementation of the protocol if it is disabled. If the TLS 1.2 implementation was disabled at build time, a TLS 1.2 client could put a TLS 1.3-only server into an infinite loop processing a TLS 1.2 ClientHello, resulting in a denial of service. If the TLS 1.2 implementation was disabled at runtime, a TLS 1.2 client can successfully establish a TLS 1.2 connection with the server.

Impact

The primary impact of CVE-2024-28836 is denial of service against servers using vulnerable Mbed TLS versions configured to disable TLS 1.2 at build time but still accepting TLS 1.2 ClientHello messages. Attackers can remotely cause the server to enter an infinite processing loop, rendering the service unavailable to legitimate users. This can disrupt critical services that rely on Mbed TLS for TLS 1.3-only secure communications, including IoT devices, embedded systems, and network appliances. Additionally, if TLS 1.2 is disabled only at runtime, the server may unintentionally allow TLS 1.2 connections, potentially weakening security by permitting older protocol versions that are less secure. Organizations worldwide using Mbed TLS in their products or infrastructure may face service outages or policy violations. While no data confidentiality or integrity loss is directly caused, the availability impact can affect business continuity, user trust, and compliance with security standards requiring modern TLS versions.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Feb 2026, 10:30 UTC

Technical details

References

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