CVE-2026-2858
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 vulnerability was identified in wren-lang wren up to 0.4.0. This affects the function peekChar of the file src/vm/wren_compiler.c of the component Source File Parser. Such manipulation leads to out-of-bounds read. The attack needs to be performed locally. The exploit is publicly available and might be used. The project was informed of the problem early through an issue report but has not responded yet.
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 confidenceAn out-of-bounds read vulnerability exists in the peekChar function in src/vm/wren_compiler.c of the Wren language compiler up to version 0.4.0. The Source File Parser component fails to perform proper bounds checking before reading from the source buffer, allowing a local attacker to read sensitive memory contents beyond the allocated buffer boundaries.
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<= 0.4.0CVSS 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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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 Wren compiler versionRun `wrenc --version` or check the installed wren-lang package version using your package manager (e.g., `pip show wren`, `apt list --installed | grep wren`, or check the source code version file)Affected if The reported version is 0.4.0 or any earlier version (e.g., 0.3.0, 0.2.0, etc.)
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Locate the wren_compiler.c source fileSearch for the file `wren_compiler.c` in the installed Wren language package directory or source code repository, typically found under src/vm/ in the project structureAffected if The file exists in the installed version, confirming the vulnerable component is present
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Verify the peekChar function vulnerabilityExamine the peekChar function in wren_compiler.c and check if bounds checking is missing before buffer read operations (look for direct buffer access without index validation against buffer length)Affected if The function lacks proper bounds checking logic before accessing the source buffer
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Confirm source file parsing is usedDetermine if your application or tooling invokes the Wren compiler to parse source files (e.g., compiling .wren scripts, using the Wren REPL, or loading Wren modules at runtime)Affected if The Wren compiler is used to parse untrusted or externally-provided source files
You are affected if you are running Wren language compiler version 0.4.0 or earlier and use it to parse source files, since the vulnerable peekChar function in the Source File Parser lacks bounds checking.
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 dataUpdate to a patched version of wren-lang once available, or implement bounds checking in the peekChar function to ensure buffer read operations stay within allocated memory limits before accessing the source file buffer.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 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 $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-2858 — 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-2026-2858 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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