CVE-2026-34871
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 before 3.6.6 and 4.x before 4.1.0 and TF-PSA-Crypto before 1.1.0. There is a Predictable Seed in a Pseudo-Random Number Generator (PRNG).
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 · moderate confidenceMbed TLS and TF-PSA-Crypto contain a predictable seed vulnerability in their PRNG implementation. If the seed used to initialize the pseudo-random number generator can be predicted or guessed, attackers can determine the entire sequence of random values generated, undermining cryptographic operations that depend on randomness such as key generation, nonces, and session tokens.
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< 3.6.6< 1.1.0CVSS 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
- Local
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
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 Mbed TLS versionLocate the mbedtls or mbed crypto library binary or header file and query its version using the library's version API (mbedtls_version_get_number() or similar) or inspect the version macro in the installed headersAffected if The version returned is less than 3.6.6
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Identify TF-PSA-Crypto versionLocate the tf-psa-crypto library and query its version through the version API or inspect the version information in the installed headersAffected if The version returned is less than 1.1.0
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Confirm PRNG usageDetermine if the library is being used for cryptographic operations that depend on the PRNG, such as key generation, random nonces, or session tokens. Review application code that calls mbedtls_psa_random_generate() or equivalent PRNG functionsAffected if The application performs cryptographic operations requiring random values and uses the affected library version
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Inspect seed source configurationExamine how the PRNG is seeded by reviewing configuration options (MBEDTLS_ENTROPY_xxx defines in mbedtls/config.h or equivalent) and any custom entropy callbacks that provide seed materialAffected if A weak, deterministic, or predictable entropy source is configured or a custom seed is used that could be guessed
You are affected if you are using Mbed TLS version below 3.6.6 or TF-PSA-Crypto version below 1.1.0 and performing cryptographic operations that rely on the library's PRNG for randomness.
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 · scoped1.1.03.6.6
Upgrade Mbed TLS to version 3.6.6 or 4.1.0 (and later), and TF-PSA-Crypto to version 1.1.0 or later. Verify that cryptographic operations relying on the PRNG continue to function correctly after the update.
Mbed TLS 3.6.6, Mbed TLS 4.1.0, or TF-PSA-Crypto 1.1.0 depending on which product is in use
- 1. Identify the current version of Mbed TLS or TF-PSA-Crypto in your deployment by checking your dependency manifests or library files
- 2. For Mbed TLS 3.x: Upgrade to version 3.6.6 or later
- 3. For Mbed TLS 4.x: Upgrade to version 4.1.0 or later
- 4. For TF-PSA-Crypto: Upgrade to version 1.1.0 or later
- 5. Rebuild and redeploy your application with the updated library
- 6. Verify the new version is correctly loaded and functioning
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-34871 — 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-2026-34871 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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