CVE-2023-45236
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 · uneditedEDK2's Network Package is susceptible to a predictable TCP Initial Sequence Number. This vulnerability can be exploited by an attacker to gain unauthorized access and potentially lead to a loss of 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 · moderate confidenceEDK2's Network Package implements a predictable TCP Initial Sequence Number (ISN) generation mechanism. Attackers can exploit this weakness to perform TCP sequence number prediction attacks, potentially hijacking existing TCP connections or impersonating servers, leading to unauthorized access and loss of confidentiality.
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<= 202311CVSS 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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/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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Identify EDK2 version in your firmwareCheck your system's firmware version information, UEFI BIOS version, or examine the EDK2 build artifacts. The EDK2 version is typically documented in the firmware release notes or can be found in the compiled EDK2 binaries.Affected if The EDK2 version is 202311 or earlier
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Confirm the Network Package is presentVerify that your EDK2 firmware includes the Network Package (NetLib). This is typically included in UEFI firmware builds that support network boot or network stack features.Affected if Network Package is included in the build and TCP networking is available
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Determine if TCP networking is enabledCheck your UEFI/BIOS settings or firmware configuration to see if TCP/IP network stack, network boot (PXE), or any network services are enabled.Affected if TCP/IP networking or network boot features are enabled in the firmware
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Inspect TCP ISN generation codeFor source code audits: examine the EDK2 Network Package source code, specifically the Tcp4Io.c or Tcp6Io.c files, and look for the ISN generation routine. Check if it uses a cryptographically secure random number generator or a predictable method.Affected if The ISN generation uses a non-random or predictable algorithm rather than a secure RNG like CTR_DRBG or HMAC_DRBG
You are affected if your system runs EDK2 firmware version 202311 or earlier with the Network Package and TCP networking enabled.
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 · scopedImplement cryptographically secure random TCP Initial Sequence Number generation using a proper random number generator (e.g., CTR_DRBG or HMAC_DRBG) in the EDK2 network stack to replace the predictable ISN generation.
EDK2 version 202312 or later stable release
- Identify the current EDK2 version in use by checking the firmware build configuration or platform documentation
- Obtain a stable EDK2 release newer than 202311 (such as 202312 or later stable release) from the official EDK2 GitHub repository at github.com/tianocore/edk2
- Update the EDK2 Network Package component to the newer version by integrating the updated package into the firmware build tree
- Rebuild the firmware image with the updated Network Package
- Deploy the updated firmware to affected systems and verify the TCP ISN generation now uses cryptographically secure random numbers
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation12.0 h
- Implementation40.0 h
- Testing24.0 h
- Review / QA16.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-45236 — 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-2023-45236 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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