---
title: "CVE-2023-44487: HTTP/2 Rapid Reset Attack Vulnerability"
url: https://erroneo.us/security/cve/CVE-2023-44487/
description: "CVE-2023-44487 (IETF HTTP/2): Exploited in the wild (CISA KEV). The HTTP/2 protocol allows a denial of service (server resource consumption) because request…"
type: vulnerability-record
section: "Security Digest"
date_published: 2023-10-10
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2023-44487"
kev: true
cvss: 7.5
epss: 0.99999
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2023-44487: HTTP/2 Rapid Reset Attack Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run IETF HTTP/2. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2023-10-10, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2023-10-31 ; treat that as the outer limit, not the target.
- EPSS 100.0% , percentile 100.0: FIRST’s model estimates a 100.0% chance of exploitation activity in the next 30 days, higher than 100.0% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Check exposure. HTTP/2 Rapid Reset: Record DDoS Flaw in HTTP/2 Servers — This is availability-only and was exploited at record scale, but if your HTTP/2 traffic terminates at a major CDN or cloud load balancer the provider already absorbed it; check what terminates HTTP/2 on your own servers.

## What it is

The HTTP/2 protocol allows a denial of service (server resource consumption) because request cancellation can reset many streams quickly, as exploited in the wild in August through October 2023.

## Affected products (CVE record)

- n/a n/a: see advisory

## Severity

- CISA-ADP CVSS 3.1: 7.5 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

## Exploitation

- CISA KEV: added 2023-10-10; federal due date 2023-10-31. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 100.00% probability of exploitation activity in the next 30 days; percentile 100.0.

## Sources

- [DSA-5522](https://www.debian.org/security/2023/dsa-5522)
- [DSA-5521](https://www.debian.org/security/2023/dsa-5521)
- [FEDORA-2023-ed2642fd58](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JMEXY22BFG5Q64HQCM5CK2Q7KDKVV4TY/)
- [FEDORA-2023-54fadada12](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZKQSIKIAT5TJ3WSLU3RDBQ35YX4GY4V3/)
- [FEDORA-2023-5ff7bf1dd8](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JIZSEFC3YKCGABA2BZW6ZJRMDZJMB7PJ/)
- [FEDORA-2023-17efd3f2cd](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WLPRQ5TWUQQXYWBJM7ECYDAIL2YVKIUH/)
- [FEDORA-2023-d5030c983c](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/E72T67UPDRXHIDLO3OROR25YAMN4GGW5/)
- [FEDORA-2023-0259c3f26f](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BFQD3KUEMFBHPAPBGLWQC34L4OWL5HAZ/)
- [FEDORA-2023-2a9214af5f](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZLU6U2R2IC2K64NDPNMV55AUAO65MAF4/)
- [FEDORA-2023-e9c04d81c1](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/X6QXN4ORIVF6XBW4WWFE7VNPVC74S45Y/)
- [FEDORA-2023-f66fc0f62a](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LKYHSZQFDNR7RSA7LHVLLIAQMVYCUGBG/)
- [FEDORA-2023-4d2fd884ea](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FNA62Q767CFAFHBCDKYNPBMZWB7TWYVU/)
- [FEDORA-2023-b2c50535cb](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LNMZJCDHGLJJLXO4OXWJMTVQRNWOC7UL/)
- [FEDORA-2023-fe53e13b5b](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KSEGD2IWKNUO3DWY4KQGUQM5BISRWHQE/)
- [Listed in CISA KEV notes (blog.cloudflare.com)](https://blog.cloudflare.com/technical-breakdown-http2-rapid-reset-ddos-attack/)
- [CVE.org record CVE-2023-44487](https://www.cve.org/CVERecord?id=CVE-2023-44487)
- [NVD entry CVE-2023-44487](https://nvd.nist.gov/vuln/detail/CVE-2023-44487)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-44487)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/alerts/2023/10/10/http2-rapid-reset-vulnerability-cve-2023-44487)
- [github.com](https://github.com/dotnet/core/blob/e4613450ea0da7fd2fc6b61dfb2c1c1dec1ce9ec/release-notes/6.0/6.0.23/6.0.23.md?plain=1#L73)
- [aws.amazon.com](https://aws.amazon.com/security/security-bulletins/AWS-2023-011/)
- [cloud.google.com](https://cloud.google.com/blog/products/identity-security/how-it-works-the-novel-http2-rapid-reset-ddos-attack)
- [nginx.com](https://www.nginx.com/blog/http-2-rapid-reset-attack-impacting-f5-nginx-products/)
- [cloud.google.com](https://cloud.google.com/blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peaking-above-398-million-rps/)
- [news.ycombinator.com](https://news.ycombinator.com/item?id=37831062)
- [blog.cloudflare.com](https://blog.cloudflare.com/zero-day-rapid-reset-http2-record-breaking-ddos-attack/)
- [phoronix.com](https://www.phoronix.com/news/HTTP2-Rapid-Reset-Attack)
- [github.com](https://github.com/envoyproxy/envoy/pull/30055)
- [github.com](https://github.com/haproxy/haproxy/issues/2312)
- [github.com](https://github.com/eclipse/jetty.project/issues/10679)
- [forums.swift.org](https://forums.swift.org/t/swift-nio-http2-security-update-cve-2023-44487-http-2-dos/67764)
- [github.com](https://github.com/nghttp2/nghttp2/pull/1961)
- [github.com](https://github.com/netty/netty/commit/58f75f665aa81a8cbcf6ffa74820042a285c5e61)
- [github.com](https://github.com/alibaba/tengine/issues/1872)
- [github.com](https://github.com/apache/tomcat/tree/main/java/org/apache/coyote/http2)
- [news.ycombinator.com](https://news.ycombinator.com/item?id=37830987)
- [news.ycombinator.com](https://news.ycombinator.com/item?id=37830998)
- [github.com](https://github.com/caddyserver/caddy/issues/5877)
- [bleepingcomputer.com](https://www.bleepingcomputer.com/news/security/new-http-2-rapid-reset-zero-day-attack-breaks-ddos-records/)
- [github.com](https://github.com/bcdannyboy/CVE-2023-44487)
- [github.com](https://github.com/grpc/grpc-go/pull/6703)
- [github.com](https://github.com/icing/mod_h2/blob/0a864782af0a942aa2ad4ed960a6b32cd35bcf0a/mod_http2/README.md?plain=1#L239-L244)
- [github.com](https://github.com/nghttp2/nghttp2/releases/tag/v1.57.0)
- [mailman.nginx.org](https://mailman.nginx.org/pipermail/nginx-devel/2023-October/S36Q5HBXR7CAIMPLLPRSSSYR4PCMWILK.html)
- [my.f5.com](https://my.f5.com/manage/s/article/K000137106)
- [msrc.microsoft.com](https://msrc.microsoft.com/blog/2023/10/microsoft-response-to-distributed-denial-of-service-ddos-attacks-against-http/2/)
- [bugzilla.proxmox.com](https://bugzilla.proxmox.com/show_bug.cgi?id=4988)
- [cgit.freebsd.org](https://cgit.freebsd.org/ports/commit/?id=c64c329c2c1752f46b73e3e6ce9f4329be6629f9)
- [[oss-security] 20231010 Re: CVE-2023-44487: HTTP/2 Rapid Reset attack against many implementations](http://www.openwall.com/lists/oss-security/2023/10/10/7)
- [[oss-security] 20231010 CVE-2023-44487: HTTP/2 Rapid Reset attack against many implementations](http://www.openwall.com/lists/oss-security/2023/10/10/6)
- [seanmonstar.com](https://seanmonstar.com/post/730794151136935936/hyper-http2-rapid-reset-unaffected)
- [github.com](https://github.com/microsoft/CBL-Mariner/pull/6381)
- [groups.google.com](https://groups.google.com/g/golang-announce/c/iNNxDTCjZvo)
- [github.com](https://github.com/facebook/proxygen/pull/466)
- [gist.github.com](https://gist.github.com/adulau/7c2bfb8e9cdbe4b35a5e131c66a0c088)
- [github.com](https://github.com/micrictor/http2-rst-stream)
- [edg.io](https://edg.io/lp/blog/resets-leaks-ddos-and-the-tale-of-a-hidden-cve)
- [openssf.org](https://openssf.org/blog/2023/10/10/http-2-rapid-reset-vulnerability-highlights-need-for-rapid-response/)
- [github.com](https://github.com/h2o/h2o/security/advisories/GHSA-2m7v-gc89-fjqf)
- [github.com](https://github.com/h2o/h2o/pull/3291)
- [github.com](https://github.com/nodejs/node/pull/50121)
- [github.com](https://github.com/dotnet/announcements/issues/277)
- [github.com](https://github.com/golang/go/issues/63417)
- [github.com](https://github.com/advisories/GHSA-vx74-f528-fxqg)
- [github.com](https://github.com/apache/trafficserver/pull/10564)
- [msrc.microsoft.com](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-44487)
- [tomcat.apache.org](https://tomcat.apache.org/security-10.html#Fixed_in_Apache_Tomcat_10.1.14)
- [lists.apache.org](https://lists.apache.org/thread/5py8h42mxfsn8l1wy6o41xwhsjlsd87q)
- [openwall.com](https://www.openwall.com/lists/oss-security/2023/10/10/6)
- [haproxy.com](https://www.haproxy.com/blog/haproxy-is-not-affected-by-the-http-2-rapid-reset-attack-cve-2023-44487)
- [github.com](https://github.com/opensearch-project/data-prepper/issues/3474)
- [github.com](https://github.com/kubernetes/kubernetes/pull/121120)
- [github.com](https://github.com/oqtane/oqtane.framework/discussions/3367)
- [github.com](https://github.com/advisories/GHSA-xpw8-rcwv-8f8p)
- [netty.io](https://netty.io/news/2023/10/10/4-1-100-Final.html)
- [theregister.com](https://www.theregister.com/2023/10/10/http2_rapid_reset_zeroday/)
- [blog.qualys.com](https://blog.qualys.com/vulnerabilities-threat-research/2023/10/10/cve-2023-44487-http-2-rapid-reset-attack)
- [news.ycombinator.com](https://news.ycombinator.com/item?id=37837043)
- [github.com](https://github.com/kazu-yamamoto/http2/issues/93)
- [martinthomson.github.io](https://martinthomson.github.io/h2-stream-limits/draft-thomson-httpbis-h2-stream-limits.html)
- [github.com](https://github.com/kazu-yamamoto/http2/commit/f61d41a502bd0f60eb24e1ce14edc7b6df6722a1)
- [github.com](https://github.com/apache/httpd/blob/afcdbeebbff4b0c50ea26cdd16e178c0d1f24152/modules/http2/h2_mplx.c#L1101-L1113)
- [access.redhat.com](https://access.redhat.com/security/cve/cve-2023-44487)
- [github.com](https://github.com/ninenines/cowboy/issues/1615)
- [github.com](https://github.com/varnishcache/varnish-cache/issues/3996)
- [github.com](https://github.com/tempesta-tech/tempesta/issues/1986)
- [blog.vespa.ai](https://blog.vespa.ai/cve-2023-44487/)
- [github.com](https://github.com/etcd-io/etcd/issues/16740)
- [darkreading.com](https://www.darkreading.com/cloud/internet-wide-zero-day-bug-fuels-largest-ever-ddos-event)
- [istio.io](https://istio.io/latest/news/security/istio-security-2023-004/)
- [github.com](https://github.com/junkurihara/rust-rpxy/issues/97)
- [bugzilla.suse.com](https://bugzilla.suse.com/show_bug.cgi?id=1216123)
- [bugzilla.redhat.com](https://bugzilla.redhat.com/show_bug.cgi?id=2242803)
- [ubuntu.com](https://ubuntu.com/security/CVE-2023-44487)
- [community.traefik.io](https://community.traefik.io/t/is-traefik-vulnerable-to-cve-2023-44487/20125)
- [github.com](https://github.com/advisories/GHSA-qppj-fm5r-hxr3)
- [github.com](https://github.com/apache/httpd-site/pull/10)
- [github.com](https://github.com/projectcontour/contour/pull/5826)
- [github.com](https://github.com/linkerd/website/pull/1695/commits/4b9c6836471bc8270ab48aae6fd2181bc73fd632)
- [github.com](https://github.com/line/armeria/pull/5232)
- [blog.litespeedtech.com](https://blog.litespeedtech.com/2023/10/11/rapid-reset-http-2-vulnerablilty/)
- [security.paloaltonetworks.com](https://security.paloaltonetworks.com/CVE-2023-44487)
- [github.com](https://github.com/akka/akka-http/issues/4323)
- [github.com](https://github.com/openresty/openresty/issues/930)
- [github.com](https://github.com/apache/apisix/issues/10320)
- [github.com](https://github.com/Azure/AKS/issues/3947)
- [github.com](https://github.com/Kong/kong/discussions/11741)
- [github.com](https://github.com/arkrwn/PoC/tree/main/CVE-2023-44487)
- [netlify.com](https://www.netlify.com/blog/netlify-successfully-mitigates-cve-2023-44487/)
- [github.com](https://github.com/caddyserver/caddy/releases/tag/v2.7.5)
- [[debian-lts-announce] 20231013 [SECURITY] [DLA 3617-1] tomcat9 security update](https://lists.debian.org/debian-lts-announce/2023/10/msg00020.html)
- [[oss-security] 20231013 Re: CVE-2023-44487: HTTP/2 Rapid Reset attack against many implementations](http://www.openwall.com/lists/oss-security/2023/10/13/4)
- [[oss-security] 20231013 Re: CVE-2023-44487: HTTP/2 Rapid Reset attack against many implementations](http://www.openwall.com/lists/oss-security/2023/10/13/9)
- [arstechnica.com](https://arstechnica.com/security/2023/10/how-ddosers-used-the-http-2-protocol-to-deliver-attacks-of-unprecedented-size/)
- [lists.w3.org](https://lists.w3.org/Archives/Public/ietf-http-wg/2023OctDec/0025.html)
- [linkerd.io](https://linkerd.io/2023/10/12/linkerd-cve-2023-44487/)
- [[debian-lts-announce] 20231016 [SECURITY] [DLA 3621-1] nghttp2 security update](https://lists.debian.org/debian-lts-announce/2023/10/msg00023.html)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20231016-0001/)
- [[debian-lts-announce] 20231016 [SECURITY] [DLA 3617-2] tomcat9 regression update](https://lists.debian.org/debian-lts-announce/2023/10/msg00024.html)
- [[oss-security] 20231018 Vulnerability in Jenkins](http://www.openwall.com/lists/oss-security/2023/10/18/4)
- [[oss-security] 20231018 Re: CVE-2023-44487: HTTP/2 Rapid Reset attack against many implementations](http://www.openwall.com/lists/oss-security/2023/10/18/8)
- [[oss-security] 20231019 CVE-2023-45802: Apache HTTP Server: HTTP/2 stream memory not reclaimed right away on RST](http://www.openwall.com/lists/oss-security/2023/10/19/6)
- [[oss-security] 20231020 Re: CVE-2023-44487: HTTP/2 Rapid Reset attack against many implementations](http://www.openwall.com/lists/oss-security/2023/10/20/8)

---
Source page: https://erroneo.us/security/cve/CVE-2023-44487/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt