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Cap Primitives sandbox escape through symlinks in trailing-slash paths

RUSTSEC-2026-0482GHSA-HP8F-XMX4-4QRG

Exploited
No known exploitation
Fix
Fixed in 3.4.6, 4.0.3
Who is exposed
Not reported

Do first: Upgrade to a fixed version: 3.4.6, 4.0.3.

Published
Last modified
Reference
Last checked
10/100 · provisional
None on Exploit-DB, Metasploit or GitHub

Summary

Paths ending in a slash can escape the sandbox in cap-primitives, which is the crate underneath cap-std and other sandboxing crates. A symlink inside the sandbox that points outside it can be opened, so an attacker who can supply the path can read, write, list, create, remove or rename files outside the sandbox.

Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.

Read the original description

cap-primitives resolves a path inside a sandboxed directory one component at a time and opens the last component with O_NOFOLLOW, so that a symlink there cannot lead out of the directory. When the path ended in /, the resolver added the slash back to the last component before opening it. With a trailing slash the operating system no longer treats that component as the last one, so O_NOFOLLOW does not apply, the symlink is followed, and the resulting file descriptor was returned without further checks.

A symlink inside the sandbox that points outside it, such as escape -> ../outside or a link to /, can therefore be opened as escape/. If the symlink's own target ends in /, the caller's path does not need a trailing slash at all, so removing trailing slashes from untrusted input is not a workaround. The maintainers' advisory reports reads and writes outside the sandbox through open, open_dir, read_dir and canonicalize, and directory creation, removal and renames outside it through create_dir, remove_dir and rename.

This resolver is used on Windows and macOS, on FreeBSD when O_RESOLVE_BENEATH is not available, and on Linux when openat2 is not available (kernels before 5.6, or a seccomp policy that rejects it). cap-std and other crates built on cap-primitives are affected through it. Wasmtime's WASI filesystem support was affected as well; that is covered by RUSTSEC-2026-0269.

The fix stops re-adding the trailing slash and is in 3.4.6 and 4.0.3.

cve.now Index

10Pcve.now Index 10 of 100 · methodology v3 · provisional
  • Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
  • Exposure?/25Unknown. No advisory context yet
  • Reach10/20Affects crates.io packages
  • Severity?/10Unknown. No CVSS score or vendor rating
  • No patch0/5No signal

What would change the score

  • Would score about 65 if added to CISA KEV
  • Would score about 60 if CISA's SSVC rates exploitation active
  • Would score about 32 if advisories confirm default setups are exposed

How the score works · Rankings

What to do

  • Upgrade to a fixed version: 3.4.6, 4.0.3.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by RUSTSEC-2026-0482 (Paths or symlinks ending in a slash escape the sandbox), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for RUSTSEC-2026-0482 (entry last updated 2026-11-11):
Affected:
- crates.io package cap-primitives: from 0.0.0-0, fixed in 3.4.6; from 4.0.0, fixed in 4.0.3
Fixed versions: 3.4.6, 4.0.3.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: RUSTSEC-2026-0482 is not listed as of cve.now's last read.
This KEV status is for RUSTSEC-2026-0482 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (crates.io): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://rustsec.org/advisories/RUSTSEC-2026-0482.html
- https://crates.io/crates/cap-primitives
- https://github.com/bytecodealliance/cap-std/pull/419
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/RUSTSEC-2026-0482
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "RUSTSEC-2026-0482"}.

Timeline

  1. Advisory published83 days
  2. Record last updated

Affected versions

  • From 0.0.0-0 · fixed in 3.4.6; From 4.0.0 · fixed in 4.0.3

Evidence 3

Other links · 3

  1. Advisory
  2. Repository
  3. Link

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about RUSTSEC-2026-0482

Is RUSTSEC-2026-0482 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data

Which versions are affected by RUSTSEC-2026-0482?

cap-primitives (crates.io): from 0.0.0-0 before 3.4.6; from 4.0.0 before 4.0.3.Source: cve.now feed data

How do I fix RUSTSEC-2026-0482?

Upgrade to a fixed version: 3.4.6, 4.0.3.Source: cve.now feed data

Sources

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