# CVE-2021-43843: Insufficient patch for Regular Expression Denial of Service (ReDoS) to jsx-slack v4.5.1 > An attacker can cause excessive resource consumption via multibyte characters in blockquotes, leading to denial of service in the jsx-slack library. - **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 20 Dec 2021 - **Updated:** 4 Aug 2024 - **Also known as:** GHSA-hp68-xhvj-x6j6 ## What is CVE-2021-43843? CVE-2021-43843 is a medium-severity denial of service vulnerability in yhatt jsx-slack, published on 20 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description jsx-slack is a package for building JSON objects for Slack block kit surfaces from JSX. The maintainers found the patch for CVE-2021-43838 in jsx-slack v4.5.1 is insufficient tfor protection from a Regular Expression Denial of Service (ReDoS) attack. If an attacker can put a lot of JSX elements into `
` tag _with including multibyte characters_, an internal regular expression for escaping characters may consume an excessive amount of computing resources. v4.5.1 passes the test against ASCII characters but misses the case of multibyte characters. jsx-slack v4.5.2 has updated regular expressions for escaping blockquote characters to prevent catastrophic backtracking. It is also including an updated test case to confirm rendering multiple tags in `
` with multibyte characters. Weakness: CWE-400 (Uncontrolled Resource Consumption), CWE-1333 (Inefficient Regular Expression Complexity) ## Which versions are affected by CVE-2021-43843? 2 open source packages ship an affected version, including jsx-slack. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `jsx-slack` | npm | All versions | 4.5.2 | | `jsx-slack` | npm | All versions | 4.5.2 | Products: Jsx-Slack Project Jsx-Slack. ## How do I fix CVE-2021-43843? Upgrade jsx-slack to 4.5.2 or later. ## Is CVE-2021-43843 being exploited? There is no known exploitation of CVE-2021-43843 in the wild and no public exploit code. ## Other vulnerabilities in yhatt jsx-slack - [CVE-2021-43838](https://insights.sbomify.com/CVE-2021-43838/): Regular Expression Denial of Service (ReDoS) in jsx-slack (medium 5.3) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-43843 and fix it if it is affected. What it is: CVE-2021-43843 is a medium-severity denial of service vulnerability in yhatt jsx-slack, published on 20 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-43843 in the wild and no public exploit code. Affected packages and fixed versions: - jsx-slack (npm): affected all versions; fixed in 4.5.2 - jsx-slack (npm): affected all versions; fixed in 4.5.2 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-43843/ (Markdown: https://insights.sbomify.com/CVE-2021-43843/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43843 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43843 - OSV: https://osv.dev/vulnerability/CVE-2021-43843 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-43843/ Summaries are generated and may contain mistakes; the official description above is the record.