How severe is CVE-2022-31103?

CVE-2022-31103 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2022-31103?

CVE-2022-31103 affects the following packages: lettersanitizer (npm). Ecosystems affected: npm.

How do I fix CVE-2022-31103?

Update lettersanitizer to 1.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-31103 is resolved across your whole dependency graph.

How do I detect CVE-2022-31103 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lettersanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2022-31103 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2022-31103 actively exploited in the wild?

No public exploit code has been indexed for CVE-2022-31103 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2022-31103?

CVE-2022-31103 has an EPSS (Exploit Prediction Scoring System) score of 1.5%, placing it in the 75th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2022-31103?

CVE-2022-31103 is classified as CWE-754 (CWE-754). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2022-31103 published, and has it been updated?

CVE-2022-31103 was published on June 27, 2022 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

HIGH severity

CVE-2022-31103 — lettersanitizer

HIGHFix: mat-sz/lettersanitizer@96d3dfe

CVE-2022-31103 is a high-severity (CVSS 7.5) CWE-754 vulnerability in lettersanitizer. A fix is available for lettersanitizer — see the affected versions and patch details below.

Improper handling of CSS at-rules in lettersanitizer

Also known asGHSA-7r3r-gq8p-v9jj

Published

Jun 27, 2022

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2022-31103.

EPSS Exploitation Probability

via FIRST.org ↗

1.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs75th percentile — riskier than 75% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

3other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

lettersanitizernpm

129Kdownloads / week

Description

Impact

All versions of lettersanitizer below 1.0.2 are affected by a denial of service issue when processing a CSS at-rule @keyframes.

This package is depended on by react-letter, therefore everyone using react-letter is also at risk.

Patches

The problem has been patched in version 1.0.2.

Workarounds

There is no workaround besides upgrading.

References

The issue was originally reported in the react-letter repository: https://github.com/mat-sz/react-letter/issues/17

For more information

If you have any questions or comments about this advisory:

Open an issue in lettersanitizer
Email me at [email protected]

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`lettersanitizer`	all versions	1.0.2`npm install lettersanitizer@1.0.2`

Affected Products

1 product · 1 configurations

Application

lettersanitizerlettersanitizer_project

< 1.0.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lettersanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update lettersanitizer to 1.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-31103 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### Impact All versions of lettersanitizer below 1.0.2 are affected by a denial of service issue when processing a CSS at-rule `@keyframes`. This package is depended on by [react-letter](https://github.com/mat-sz/react-letter), therefore everyone using react-letter is also at risk. ### Patches The problem has been patched in version 1.0.2. ### Workarounds There is no workaround besides upgrading. ### References The issue was originally reported in the react-letter repository: https://github.com/mat-sz/react-letter/issues/17 ### For more information If you have any questions or comment