CVE-2024-28755
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn Mbed TLS 3.5.x before 3.6.0, calling the mbedtls_ssl_session_reset() API to reset an SSL context does not restore the maximum TLS version to the originally configured value. This causes the server to remain stuck at a lower TLS version capability after session reset, preventing TLS 1.3 connections from being negotiated even when TLS 1.3 is enabled in configuration.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 3.5.0, <= 3.6.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Mbed TLS versionCheck the version header file (such as include/mbedtls/version.h) or use the mbedtls_version_get_number() API to retrieve the library version numberAffected if The version is 3.5.0 or higher but lower than 3.6.0 (unpatched release)
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Verify usage of mbedtls_ssl_session_reset() APISearch source code for calls to mbedtls_ssl_session_reset() function in the application or library that uses Mbed TLSAffected if The function is called in the codebase and the SSL context is being reused for new connections after a session reset
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Confirm TLS 1.3 is enabled in configurationInspect the Mbed TLS configuration file (mbedtls_config.h) or runtime configuration to verify MBEDTLS_SSL_PROTO_TLS13 is defined or TLS 1.3 is enabledAffected if TLS 1.3 support is enabled in the Mbed TLS build configuration
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Determine if the system operates as an SSL/TLS serverReview application role - check if it accepts incoming TLS connections and uses mbedtls_ssl_session_reset() to handle session reuseAffected if The system acts as a TLS server that resets sessions and expects TLS 1.3 to be negotiated after reset
You are affected if you run Mbed TLS versions 3.5.0 through 3.6.0, use mbedtls_ssl_session_reset() in server mode, and have TLS 1.3 enabled but cannot establish TLS 1.3 connections after session reset.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade Mbed TLS to version 3.6.0 or later to obtain the fix. Additionally, monitor for unexpected TLS version downgrades as an indicator of potential exploitation.
Mbed TLS 3.6.0 or later
- Obtain Mbed TLS version 3.6.0 or later from the official repository (github.com/Mbed-TLS/mbedtls)
- Replace the existing Mbed TLS library files in your project with the new version
- Recompile and rebuild your application with the updated Mbed TLS library
- Re-test TLS functionality to confirm TLS 1.3 connections are working properly after session reset operations
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2024-28755 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2024-28755 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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