CVE-2026-45372
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 · uneditedcpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The validity check (is_field_value) is run before decoding, so encoded %0D%0A passes the check and is then expanded to a literal \r\n byte pair inside the stored header value. This vulnerability is fixed in 0.44.0.
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 cpp-httplib prior to 0.44.0, the is_field_value validity check runs BEFORE percent-decoding of header values, allowing %0D%0A (CRLF) encoded sequences to pass validation and then expand to literal carriage return and newline bytes. This enables HTTP Response Splitting/CRLF injection attacks where malicious headers can be injected into HTTP requests.
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< 0.44.0CVSS 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
- Changed
- Confidentiality
- Low
- Integrity
- High
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/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 cpp-httplib usage in your applicationSearch your codebase for '#include <httplib.h>' or '#include "httplib.h"' to confirm the library is used. Also check build configuration or dependency manifests for cpp-httplib references.Affected if cpp-httplib is present in your codebase or dependencies
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Determine installed cpp-httplib versionOpen the httplib.h header file and locate the version definition (typically HTTPLIB_VERSION or similar macro near the top of the file). Compare the version number to 0.44.0.Affected if The version is less than 0.44.0 or the version cannot be determined
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Verify HTTP request parsing is enabledConfirm your application uses the library's server functionality (httplib::Server) to handle incoming HTTP requests. Check for instantiation of httplib::Server and registered handlers (Get, Post, etc.).Affected if Your application uses cpp-httplib as an HTTP server to parse incoming requests
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Check for input validation on incoming header valuesReview your code or middleware that processes incoming HTTP request headers. Look for validation logic that rejects header values containing encoded newline sequences (%0D%0A, %0A, %0D) before the library processes them.Affected if No input validation exists for header values containing encoded newline sequences and the version is below 0.44.0
You are affected if your application uses cpp-httplib as an HTTP server with a version below 0.44.0 and processes incoming requests without additional input validation that rejects encoded newline sequences in header values.
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 · scoped0.44.0
Upgrade cpp-httplib to version 0.44.0 or later, which applies the validity check after percent-decoding. If immediate upgrade is not feasible, implement input validation to reject headers containing raw or encoded CRLF sequences before processing.
0.44.0
- Identify all deployments and builds using cpp-httplib library version less than 0.44.0
- Update the cpp-httplib header file (httplib.h) or dependency to version 0.44.0 or later
- Rebuild all affected applications and services that depend on the updated library
- Redeploy the rebuilt applications
- Verify the fix by testing that percent-encoded %0D%0A in HTTP header values is no longer expanded to literal CRLF characters
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-45372 — 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-2026-45372 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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