VirtualizationApplication · Redhat
CVE-2020-25657
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 · uneditedA flaw was found in all released versions of m2crypto, where they are vulnerable to Bleichenbacher timing attacks in the RSA decryption API via the timed processing of valid PKCS#1 v1.5 Ciphertext. The highest threat from this vulnerability is to confidentiality.
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 m2crypto Python library contains a timing side-channel vulnerability in its RSA decryption API. The library exhibits detectable timing differences when processing valid versus invalid PKCS#1 v1.5 padding, allowing an attacker to perform a Bleichenbacher-style oracle attack to gradually decrypt RSA-encrypted data over many observed decryption operations.
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
VirtualizationApplication
= 4.0
Enterprise LinuxOperating system
= 6.0= 7.0
FedoraOperating system
= 33all versionsCVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/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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Verify M2crypto is installedRun 'pip show m2crypto' or 'python -c "import m2crypto; print(m2crypto.__version__)"'Affected if M2crypto is present and the version cannot be determined or is any version
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Identify RSA decryption usage in codeSearch source code for patterns like 'm2crypto.RSA', 'rsa_decrypt', 'private_decrypt', or 'PKCS1_v1_5' padding usage in decryption contextsAffected if Code uses M2crypto's RSA decryption functions with PKCS#1 v1.5 padding
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Check for exposure to untrusted RSA-encrypted inputReview application logic to determine if RSA decryption processes data from network sources, external APIs, or untrusted users that could be observed over multiple operationsAffected if RSA decryption processes ciphertext from attackers who can measure response times
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Confirm RSA padding scheme in useExamine decryption code for the padding parameter; PKCS1_OAEP or PKCS1_AFU are resistant, but PKCS1_v1_5 is vulnerableAffected if The code explicitly uses PKCS#1 v1.5 padding (PKCS1_padding or no padding specified) for RSA decryption
You are affected if M2crypto is installed and your application uses its RSA decryption API with PKCS#1 v1.5 padding on data from attackers who can observe timing differences across multiple decryption attempts.
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.
From vendor dataReplace PKCS#1 v1.5 padding with OAEP (Optimal Asymmetric Encryption Padding) for RSA decryption, or implement constant-time decryption routines to eliminate timing variations.
Fix this in Virtualization
Scoped from the published advisory
- 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-2020-25657 — 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-2020-25657 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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