Node.js: Heap buffer overflow in HTTP/2 session.altsvc() via long origin
Summary
A one-byte heap buffer overflow in the HTTP/2 Alt-Svc handling of Node.js lets a remote, unauthenticated attacker corrupt process memory. It only applies when an application passes attacker-controlled input, such as a request's :authority header, to Http2Session.altsvc(). A single request with a long but syntactically valid :authority can abort the process and serves as a remote heap-corruption primitive. The CVSS vector assigns no confidentiality impact.
Affected
- Node.js 24.0.0 to before 24.22.3
- Node.js 25.0.0 to before 26.13.1 (end-of-life line)
- Node.js 26.x before 26.13.1
- Node.js 22.x: Unknown.
Fixed in
- Node.js 26.13.1
- Node.js 24.22.3 (first unaffected version listed in the CNA record)
Workaround
- Unknown. No workaround is listed in the CVE record.
- Until patched, review applications that pass request headers such as :authority to altsvc() and remove or validate this pattern.
Exploitation
- No known exploitation as of 11 Nov 2026.
- No public exploit or proof of concept found as of 11 Nov 2026.
- Not listed in CISA KEV.
- VulDB marks the status as 0-day with no exploit available.
Our recommendation
- Inventory all Node.js runtimes, including those in containers, appliances and vendor products.
- Upgrade to Node.js 26.13.1 or 24.22.3, and replace end-of-life versions.
- Check whether any application passes request headers to altsvc() and prioritise those applications.
- Patch the complete Node.js runtime, as this release also fixes several other High-rated HTTP/2 and TLS issues.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- OpenJS CNA security advisories cna.openjsf.org
- Node.js November 2026 security releases nodejs.org
- CVE Record CVE-2026-123828 www.cve.org
- Node.js 26.13.1 release nodejs.org
- VulDB CVE-2026-123828 vuldb.com
- OffSeq threat entry CVE-2026-123828 radar.offseq.com
- Strix CVE-2026-123828 www.strix.ai
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 20:44.
Original description (NVD)
A one-byte heap buffer overflow in Node.js HTTP/2 Alt-Svc handling lets a remote, unauthenticated attacker corrupt process memory. When an application passes an attacker-controlled value such as a request's :authority header to Http2Session.altsvc(), the AltSvc implementation in src/node_http2.cc allocates a buffer sized to the origin length and then writes it with a null terminator, placing one byte past the end of the allocation. A single request carrying a long but syntactically valid :authority triggers the out-of-bounds write, which aborts the process and serves as a remote heap-corruption primitive. This vulnerability affects Node.js 26.x and 24.x.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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