CVE-2024-28755Public exploitNetwork attack vector

TLS 1.3 denial and downgrade via incomplete reset

Published Apr 3, 2024 · Updated Sep 6, 2024

Denial of service in TrustedFirmware.org Mbed TLS before 3.6.0 allows remote attackers to block TLS 1.3 after a TLS 1.2 session. mbedtls_ssl_session_reset() fails to restore the configured maximum TLS version, leaving the prior TLS 1.2 negotiation limit in the reused SSL context. A server must reuse a reset SSL context with TLS 1.3 enabled; later TLS 1.3 handshakes fail, interrupting service or forcing TLS 1.2.

CVSS severity6.5
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in TrustedFirmware.org Mbed TLS before 3.6.0 allows remote attackers to block TLS 1.3 after a TLS 1.2 session. mbedtls_ssl_session_reset() fails to restore the configured maximum TLS version, leaving the prior TLS 1.2 negotiation limit in the reused SSL context. A server must reuse a reset SSL context with TLS 1.3 enabled; later TLS 1.3 handshakes fail, interrupting service or forcing TLS 1.2.

The record

CVE
CVE-2024-28755
Published
Apr 3, 2024
Updated
Sep 6, 2024
Vendor
TrustedFirmware.org
Product
Mbed TLS
Classifications
CWE-326, T1499, T1562.010
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 3, 2024CVE publishedPublication date reported by the CVE source.
  2. Sep 6, 2024Record 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=0 <3.6.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

TrustedFirmware.org · Mbed TLSversion=0 <3.6.0

Published CVSS scores

6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-326Inadequate Encryption Strength
T1499Endpoint Denial of Service
T1562.010Downgrade Attack

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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