GHSA-7cg8-pq9v-x98q
Sandbox Breakout in realms-shim
GHSA-7cg8-pq9v-x98q is a critical vulnerability (CVSS 9.8) in realms-shim, published October 21, 2019. No source lists public exploit code. Fixed in realms-shim 1.2.1.
- Severity
- 9.8 CriticalCVSS 3.1, GitHub Advisories
- Exploit chance
- UnscoredNo EPSS score yet
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
1.2.1realms-shim
Description
Versions of realms-shim prior to 1.2.1 are vulnerable to a Sandbox Breakout. The Realms evaluation function has an option to apply Babel-like transformations to the source code before it reaches the evaluator. One portion of this transform pipeline exposed a primal-Realm object to the rewriting function. Confined code which used the evaluator itself could provide a malicious rewriter function that captured this object, and use it to breach the sandbox.
Recommendation
Upgrade to version 1.2.1 or later.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Affected packages
| Package | Affected | Fixed |
|---|---|---|
realms-shimnpm | before 1.2.1 | 1.2.1 |
What each source reports
GitHub Advisories Score used
Sandbox Breakout in realms-shim
Versions of realms-shim prior to 1.2.1 are vulnerable to a Sandbox Breakout. The Realms evaluation function has an option to apply Babel-like transformations to the source code before it reaches the evaluator. One portion of this transform pipeline exposed a primal-Realm object to the rewriting function. Confined code which used the evaluator itself could provide a malicious rewriter function that captured this object, and use it to breach the sandbox.
Recommendation
Upgrade to version 1.2.1 or later.
- Record
GHSA-7cg8-pq9v-x98q- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSV
Sandbox Breakout in realms-shim
Versions of realms-shim prior to 1.2.1 are vulnerable to a Sandbox Breakout. The Realms evaluation function has an option to apply Babel-like transformations to the source code before it reaches the evaluator. One portion of this transform pipeline exposed a primal-Realm object to the rewriting function. Confined code which used the evaluator itself could provide a malicious rewriter function that captured this object, and use it to breach the sandbox.
Recommendation
Upgrade to version 1.2.1 or later.
- Record
GHSA-7cg8-pq9v-x98q- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | GitHub Advisories, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.