shescape: Inefficient Regular Expression Complexity
CVE-2022-36064 is a high-severity inefficient regular expression complexity vulnerability in shescape from Ericcornelissen, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected shescape versions: >= 1.5.1, < 1.5.10. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.46% chance of exploitation within 30 days, higher than 74% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of shescape you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Ericcornelissen | shescape | >= 1.5.1, < 1.5.10 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.9 | Medium | CNA (github.com) |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
Shescape is a shell escape package for JavaScript. An Inefficient Regular Expression Complexity vulnerability impacts users that use Shescape to escape arguments for the Unix shells `Bash` and `Dash`, or any not-officially-supported Unix shell; and/or using the `escape` or `escapeAll` functions with the `interpolation` option set to `true`. An attacker can cause polynomial backtracking or quadratic runtime in terms of the input string length due to two Regular Expressions in Shescape that are vulnerable to Regular Expression Denial of Service (ReDoS). This bug has been patched in v1.5.10. For `Dash` only, this bug has been patched since v1.5.9. As a workaround, a maximum length can be enforced on input strings to Shescape to reduce the impact of the vulnerability. It is not recommended to try and detect vulnerable input strings, as the logic for this may end up being vulnerable to ReDoS itself.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Inefficient Regular Expression Complexity
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
How developers prevent this class of flaw
- Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
- Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
- Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
More Inefficient Regular Expression Complexity vulnerabilities (CWE-1333)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/ericcornelissen/shescape/security/advisories/GHSA-gp75-h7j6-5pv3Exploit, Issue Tracking, Mitigation, Third Party Advisory
Patches and release notes
- github.com/ericcornelissen/shescape/pull/373Issue Tracking, Third Party Advisory
- github.com/ericcornelissen/shescape/releases/tag/v1.5.10Release Notes, Third Party Advisory
Other vulnerabilities in shescape
- 9.2 Critical severity
- 8.7 High severity
- 8.6 High severity
- 9.8 Critical severity
- 9.8 Critical severity
Recent Inefficient Regular Expression Complexity vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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