CVE-2025-49601
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 · uneditedIn MbedTLS 3.3.0 before 3.6.4, mbedtls_lms_import_public_key does not check that the input buffer is at least 4 bytes before reading a 32-bit field, allowing a possible out-of-bounds read on truncated input. Specifically, an out-of-bounds read in mbedtls_lms_import_public_key allows context-dependent attackers to trigger a crash or limited adjacent-memory disclosure by supplying a truncated LMS (Leighton-Micali Signature) public-key buffer under four bytes. An LMS public key starts with a 4-byte type indicator. The function mbedtls_lms_import_public_key reads this type indicator before validating the size of its input.
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 confidenceThe mbedtls_lms_import_public_key function in MbedTLS reads a 4-byte type indicator from an input buffer before validating that the buffer is large enough, allowing an out-of-bounds read when supplied truncated LMS public-key input under 4 bytes. This can cause crashes or limited adjacent-memory disclosure.
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>= 3.3.0, < 3.6.4CVSS 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
- Low
- Integrity
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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 MbedTLS versionCheck the version header file (mbedtls_version.h) or library binary metadata. Common locations: /usr/include/mbedtls/mbedtls_version.h or check library files like libmbedtls.so with 'strings' or 'objdump -s' for version strings.Affected if Version is 3.3.0 through 3.6.3 (inclusive)
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Verify LMS support is compiled inCheck if the MbedTLS build includes LMS support by searching for MBEDTLS_LMS_C preprocessor macro in build configuration, or check for presence of lms.c file in the compiled library with 'nm libmbedtls.a | grep lms' or equivalent.Affected if LMS support is enabled in the build (the vulnerable function only exists when LMS is compiled)
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Search for usage of mbedtls_lms_import_public_keySearch source code repositories for calls to mbedtls_lms_import_public_key function using grep: 'grep -r "mbedtls_lms_import_public_key"' across project source files.Affected if Code calls this function to import LMS public keys
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Check LMS input buffer validationReview code paths that feed buffers to mbedtls_lms_import_public_key. Verify if buffers are checked to be at least 4 bytes before the function call. Look for length checks like 'if (buf_len < 4)' or similar validation.Affected if LMS public-key buffers are passed without prior minimum-length validation (under 4 bytes triggers the out-of-bounds read)
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Inspect runtime memory handling of LMS keysIf instrumentation is available, monitor mbedtls_lms_import_public_key calls with AddressSanitizer or valgrind when processing LMS public keys. Check for out-of-bounds read warnings.Affected if Truncated LMS keys (under 4 bytes) cause out-of-bounds memory access
You are affected if you use MbedTLS version 3.3.0-3.6.3 with LMS support enabled and pass LMS public-key buffers to mbedtls_lms_import_public_key without first validating they are at least 4 bytes long.
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 · scoped3.6.4
Upgrade MbedTLS to version 3.6.4 or later which adds proper bounds checking before reading the type indicator field. If upgrade is not immediately feasible, ensure all LMS public-key buffers passed to this function are validated to be at least 4 bytes beforehand.
3.6.4
- Identify where Mbed TLS is used in your project (check package.json, Cargo.toml, requirements.txt, conanfile.txt, or submodule references)
- Verify the current Mbed TLS version is >= 3.3.0 and < 3.6.4 by examining your lock file or installed packages
- Update your dependency specification to require Mbed TLS version 3.6.4 or later (e.g., change version constraint to ">=3.6.4")
- Regenerate lock files and reinstall dependencies
- Rebuild the project to link against the updated Mbed TLS library
- Run your test suite to verify functionality is unchanged
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-49601 — 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-2025-49601 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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- Version or environment caveats, and links to real fixes
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