CVE-2026-38640
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 reachable unwrap in the __assert_fail function (/assert/mod.rs) of relibc commit 61f42d allows attackers to cause a Denial of Service (DoS) via a crafted string.
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 confidenceA reachable unwrap() in the __assert_fail function of relibc's assertion handling module allows a crafted string input to trigger a panic, causing denial of service. The vulnerability stems from improper error handling where an unwrap operation assumes string input validity without defensive checks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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 if relibc is in useSearch for relibc in project dependencies (Cargo.toml, Cargo.lock, or embedded system configurations) or check if the codebase contains relibc source filesAffected if relibc is present in the environment
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Locate the assertion handling moduleSearch for the file assert/mod.rs or __assert_fail function definition within the relibc source treeAffected if The assertion module exists and is compiled into the binary
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Check for vulnerable unwrap patternExamine the __assert_fail function source code for unwrap() calls on string input without prior validationAffected if An unwrap() on string data is present without defensive checks before it
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Determine if assertion input is externally controllableTrace data flow to identify if user-supplied or network-provided strings can reach the assertion handlerAffected if Untrusted input can reach the __assert_fail function without sanitization
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Verify the build includes assertion handling codeCheck if assertion debugging is enabled in the build (assertions are typically compiled in debug builds or when debugging flags are set)Affected if The binary includes compiled assertion handling code from relibc
The environment is affected if relibc is present, the __assert_fail function contains an unwrap() on potentially untrusted string input, and that input can be controlled by an attacker.
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 the unwrap() with proper error handling (e.g., match, if let, or expect with meaningful error messages) in the assert/mod.rs file to gracefully handle malformed input instead of panicking.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-38640 — 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-2026-38640 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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