CVE-2023-44487
HTTP/2 Rapid Reset
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.
- CVSS
- 7.5Highscored by CISA
- Exploited in the wild
- Yes, in CISA KEV since 10 Oct 2023CISA deadline for US federal agencies: 31 Oct 2023public exploit code
- EPSS
- > 99.9%chance of exploitation in the next 30 daystop 0.1% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Fixed in 8.5.94, 9.0.81, 10.1.14per the vendor; 18 more listed below
- Published
- 10 Oct 2023analysed here 12 Nov 2026
Do first. Upgrade to a fixed release: 8.5.94, 9.0.81, 10.1.14, 3.6.1 (and 17 more below).
Summary
Triage
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Apache Tomcatfrom the Bitnami advisory, via OSV | >= 8.5.0 and < 8.5.94>= 9.0.0 and < 9.0.81>= 10.0.0 and < 10.1.14Vendor says fixed in: 8.5.94, 9.0.81, 10.1.14 | |
| apisixfrom the Bitnami advisory, via OSV | < 3.6.1Vendor says fixed in: 3.6.1 | |
| ASP.NET Corefrom the Bitnami advisory, via OSV | >= 6.0.0 and < 6.0.23>= 7.0.0 and < 7.0.12Vendor says fixed in: 6.0.23, 7.0.12 | |
| contourfrom the Bitnami advisory, via OSV | < 1.24.6Vendor says fixed in: 1.24.6 | |
| envoyfrom the Bitnami advisory, via OSV | < 1.24.12>= 1.25.0 and < 1.25.11>= 1.26.0 and < 1.26.6>= 1.27.0 and < 1.27.2Vendor says fixed in: 1.24.12, 1.25.11, 1.26.6, 1.27.2 | |
| jenkinsfrom the Bitnami advisory, via OSV | < 2.414.3>= 2.415.0 and < 2.428.0Vendor says fixed in: 2.414.3, 2.428.0 | |
| kongfrom the Bitnami advisory, via OSV | < 3.4.2Vendor says fixed in: 3.4.2 | |
| .NETfrom the Bitnami advisory, via OSV | >= 6.0.0 and < 6.0.23>= 7.0.0 and < 7.0.12Vendor says fixed in: 6.0.23, 7.0.12 | |
| .NET SDKfrom the Bitnami advisory, via OSV | >= 6.0.0 and < 6.0.23>= 7.0.0 and < 7.0.12Vendor says fixed in: 6.0.23, 7.0.12 | |
| nginxfrom the Bitnami advisory, via OSV | >= 1.9.5 and < 1.25.3Vendor says fixed in: 1.25.3 | |
| nginx-gatewayfrom the Bitnami advisory, via OSV | >= 1.9.5 and < 1.25.3Vendor says fixed in: 1.25.3 | |
| Node.jsfrom the Node.js security advisory | >= 18.0.0 and < 18.18.2>= 20.0.0 and < 20.8.1Vendor says fixed in: 18.18.2, 20.8.1 | |
| solrfrom the Bitnami advisory, via OSV | < 9.4.0Vendor says fixed in: 9.4.0 | |
| varnishfrom the Bitnami advisory, via OSV | < 6.0.12>= 6.1.0 and < 7.3.1>= 7.4.0 and < 7.4.2Vendor says fixed in: 6.0.12, 7.3.1, 7.4.2 |
As published in the CVE Program record, and, for products that ship the affected component, in the advisory named beside them. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- siemens:simatic_s7-1500_cpu_1518f-4_pn\/dp_mfp_firmware
- siemens:sinec_ins
- siemens:sinec_nms
- siemens:st7_scadaconnect
- siemens:ruggedcom_ape1808_firmware
- siemens:simatic_s7-1500_cpu_1518-4_pn\/dp_mfp_firmware
- siemens:siplus_s7-1500_cpu_1518-4_pn\/dp_mfp_firmware
- ietf:http
- nghttp2:nghttp2
- netty:netty
- envoyproxy:envoy
- eclipse:jetty
- caddyserver:caddy
- golang:go
- golang:http2
- golang:networking
- f5:big-ip_access_policy_manager
- f5:big-ip_advanced_firewall_manager
- f5:big-ip_advanced_web_application_firewall
- f5:big-ip_analytics
- f5:big-ip_application_acceleration_manager
- f5:big-ip_application_security_manager
- f5:big-ip_application_visibility_and_reporting
- f5:big-ip_carrier-grade_nat
- f5:big-ip_ddos_hybrid_defender
- f5:big-ip_domain_name_system
- f5:big-ip_fraud_protection_service
- f5:big-ip_global_traffic_manager
- f5:big-ip_link_controller
- f5:big-ip_local_traffic_manager
Fix and mitigation
WAF and other mitigations
Can a WAF block it? Partly. The attack uses HTTP/2 request cancellation to reset many streams quickly, which is unusual traffic that a WAF could detect by monitoring rapid repeated stream resets in HTTP/2 connections. A custom WAF rule can filter many HTTP/2 stream reset frames sent quickly in one connection, but attackers can vary the request. No tracked WAF vendor has published a rule for this CVE yet.
What a custom rule would match: many HTTP/2 stream reset frames sent quickly in one connection
Also consider: patch · custom WAF rule · rate limit · CDN
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 10 Oct 2023.
- CISA due date
- 31 Oct 2023, the remediation deadline for US federal agencies
- 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.
- Public exploit code
- Yes: 1 on Exploit-DB · 26 GitHub proofs of concept
- CISA SSVC
- exploitation active, automatable yes, technical impact partialAssessed by CISA 23 Jul 2024 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Exploit-DB
- HTTP/2 2.0 - Denial Of Service (DOS)remote, 16 Sept 2025
GitHub proofs of concept
- bcdannyboy/CVE-2023-44487248 stars
- secengjeff/rapidresetclient76 stars
- imabee101/CVE-2023-4448756 stars
- studiogangster/CVE-2023-4448722 stars
and 22 more repositories
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
Timeline
- 10 Oct 2023Added to CISA KEV (exploited in the wild)
- 10 Oct 2023First public exploit or proof of conceptsame day later
- 10 Oct 2023Published1 day later
- 31 Oct 2023CISA remediation due date (US federal agencies)20 days later
- 23 Jul 2024CISA SSVC assessment: exploitation active267 days (about 9 months) later
- 14 Oct 2026CVE record last updated813 days (about 2 years) later
- 12 Nov 2026Analysed by vulneraibility.com29 days later
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
| Metric | Value | What it means |
|---|---|---|
| Attack vector | NetworkReachable over the internet or any routable network. | Reachable over the internet or any routable network. |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | NoneThe attacker needs no prior access. | The attacker needs no prior access. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | NoneNo data disclosure. | No data disclosure. |
| Integrity | NoneNo unauthorised modification. | No unauthorised modification. |
| Availability | HighFull outage possible. | Full outage possible. |
Common questions
Is CVE-2023-44487 being exploited?
Yes. CVE-2023-44487 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2023-44487?
CVE-2023-44487 is rated High with a CVSS score of 7.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2023-44487?
Yes. A fix has been recorded for CVE-2023-44487. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2023-44487 affect?
CVE-2023-44487 affects siemens:simatic_s7-1500_cpu_1518f-4_pn\/dp_mfp_firmware, siemens:sinec_ins, siemens:sinec_nms, siemens:st7_scadaconnect, and 26 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
50 references in the CVE record, grouped by the tags the record gives them.
Other links (50)
- github.com /dotnet/core/blob/e4613450ea0da7fd2fc6b61dfb2c1c1dec1ce9ec/release-notes/6.0/6.0
- blog.cloudflare.com /technical-breakdown-http2-rapid-reset-ddos-attack/
- aws.amazon.com /security/security-bulletins/AWS-2023-011/
- cloud.google.com /blog/products/identity-security/how-it-works-the-novel-http2-rapid-reset-ddos-a
- nginx.com /blog/http-2-rapid-reset-attack-impacting-f5-nginx-products/
- cloud.google.com /blog/products/identity-security/google-cloud-mitigated-largest-ddos-attack-peak
Show 44 more
- news.ycombinator.com /item?id=37831062
- blog.cloudflare.com /zero-day-rapid-reset-http2-record-breaking-ddos-attack/
- phoronix.com /news/HTTP2-Rapid-Reset-Attack
- github.com /envoyproxy/envoy/pull/30055
- github.com /haproxy/haproxy/issues/2312
- github.com /eclipse/jetty.project/issues/10679
- forums.swift.org /t/swift-nio-http2-security-update-cve-2023-44487-http-2-dos/67764
- github.com /nghttp2/nghttp2/pull/1961
- github.com /netty/netty/commit/58f75f665aa81a8cbcf6ffa74820042a285c5e61
- github.com /alibaba/tengine/issues/1872
- github.com /apache/tomcat/tree/main/java/org/apache/coyote/http2
- news.ycombinator.com /item?id=37830987
- news.ycombinator.com /item?id=37830998
- github.com /caddyserver/caddy/issues/5877
- bleepingcomputer.com /news/security/new-http-2-rapid-reset-zero-day-attack-breaks-ddos-records/
- github.com /bcdannyboy/CVE-2023-44487
- github.com /grpc/grpc-go/pull/6703
- github.com /icing/mod_h2/blob/0a864782af0a942aa2ad4ed960a6b32cd35bcf0a/mod_http2/README.md?
- github.com /nghttp2/nghttp2/releases/tag/v1.57.0
- mailman.nginx.org /pipermail/nginx-devel/2023-October/S36Q5HBXR7CAIMPLLPRSSSYR4PCMWILK.html
- my.f5.com /manage/s/article/K000137106
- msrc.microsoft.com /blog/2023/10/microsoft-response-to-distributed-denial-of-service-ddos-attacks-a
- bugzilla.proxmox.com /show_bug.cgi?id=4988
- cgit.freebsd.org /ports/commit/?id=c64c329c2c1752f46b73e3e6ce9f4329be6629f9
- openwall.com /lists/oss-security/2023/10/10/7
- openwall.com /lists/oss-security/2023/10/10/6
- seanmonstar.com /post/730794151136935936/hyper-http2-rapid-reset-unaffected
- github.com /microsoft/CBL-Mariner/pull/6381
- groups.google.com /g/golang-announce/c/iNNxDTCjZvo
- github.com /facebook/proxygen/pull/466
- gist.github.com /adulau/7c2bfb8e9cdbe4b35a5e131c66a0c088
- github.com /micrictor/http2-rst-stream
- edg.io /lp/blog/resets-leaks-ddos-and-the-tale-of-a-hidden-cve
- openssf.org /blog/2023/10/10/http-2-rapid-reset-vulnerability-highlights-need-for-rapid-resp
- github.com /h2o/h2o/security/advisories/GHSA-2m7v-gc89-fjqf
- github.com /h2o/h2o/pull/3291
- github.com /nodejs/node/pull/50121
- github.com /dotnet/announcements/issues/277
- github.com /golang/go/issues/63417
- github.com /advisories/GHSA-vx74-f528-fxqg
- github.com /apache/trafficserver/pull/10564
- msrc.microsoft.com /update-guide/vulnerability/CVE-2023-44487
- tomcat.apache.org /security-10.html#Fixed_in_Apache_Tomcat_10.1.14
- lists.apache.org /thread/5py8h42mxfsn8l1wy6o41xwhsjlsd87q
Also tracked as GHSA-2m7v-gc89-fjqf, GHSA-qppj-fm5r-hxr3, GHSA-vx74-f528-fxqg, GHSA-xpw8-rcwv-8f8p, GO-2023-2102, GO-2023-2153 (OSV).
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Exploit-DB: published exploits
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
- OSV: advisory aliases and downstream package versions
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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