CVE-2026-21637
published 2026-01-20CVE-2026-21637: A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use…
PriorityP343high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
1.06%
60.7th percentile
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
Affected
26 ranges· showing 25
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | nodejs | < nodejs 22.22.2+dfsg+~cs22.19.15-1 (forky) | nodejs 22.22.2+dfsg+~cs22.19.15-1 (forky) |
| nodejs | node | >= 10.0 < 10.* | 10.* |
| nodejs | node | >= 11.0 < 11.* | 11.* |
| nodejs | node | >= 12.0 < 12.* | 12.* |
| nodejs | node | >= 13.0 < 13.* | 13.* |
| nodejs | node | >= 14.0 < 14.* | 14.* |
| nodejs | node | >= 15.0 < 15.* | 15.* |
| nodejs | node | >= 16.0 < 16.* | 16.* |
| nodejs | node | >= 17.0 < 17.* | 17.* |
| nodejs | node | >= 18.0 < 18.* | 18.* |
| nodejs | node | 20.19.6 – 20.19.6 | — |
| nodejs | node | 22.21.1 – 22.21.1 | — |
| nodejs | node | 24.12.0 – 24.12.0 | — |
| nodejs | node | 25.2.1 – 25.2.1 | — |
| nodejs | node | >= 4.0 < 4.* | 4.* |
| nodejs | node | >= 5.0 < 5.* | 5.* |
| nodejs | node | >= 6.0 < 6.* | 6.* |
| nodejs | node | >= 7.0 < 7.* | 7.* |
| nodejs | node | >= 8.0 < 8.* | 8.* |
| nodejs | node | >= 9.0 < 9.* | 9.* |
| nodejs | node.js | >= 22.0.0 < 22.22.0 | 22.22.0 |
| nodejs | node.js | >= 24.0.0 < 24.13.0 | 24.13.0 |
| nodejs | node.js | >= 25.0.0 < 25.3.0 | 25.3.0 |
| nodejs | node.js | >= 4.0.0 < 20.20.0 | 20.20.0 |
| nodejs | nodejs | >= 0 < 20.19.2+dfsg-1+deb13u2 | 20.19.2+dfsg-1+deb13u2 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv3.05.9MEDIUMCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
osv7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
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GHSA
GHSA-ggxc-26fx-987r: A flaw in Node
ghsa_unreviewed·2026-01-20
CVE-2026-21637 [MEDIUM] CWE-400 GHSA-ggxc-26fx-987r: A flaw in Node
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
OSV
CVE-2026-21637: A flaw in Node
osv·2026-01-20·CVSS 7.5
CVE-2026-21637 [HIGH] CVE-2026-21637: A flaw in Node
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
Red Hat
nodejs: Nodejs denial of service
vendor_redhat·2026-01-20·CVSS 7.5
CVE-2026-21637 [HIGH] CWE-248 nodejs: Nodejs denial of service
nodejs: Nodejs denial of service
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust res
Debian
CVE-2026-21637: nodejs - A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust...
vendor_debian·2026·CVSS 7.5
CVE-2026-21637 [HIGH] CVE-2026-21637: nodejs - A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust...
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
Scope: local
bookworm: open
bullseye: open
forky: resolved (fixed in 22.22.2+dfsg+~cs22.19.15-1)
sid: resolved (fixed i
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-21637 nodejs18: Nodejs denial of service [fedora-42]
bugzilla·2026-01-21·CVSS 7.5
CVE-2026-21637 [HIGH] CVE-2026-21637 nodejs18: Nodejs denial of service [fedora-42]
CVE-2026-21637 nodejs18: Nodejs denial of service [fedora-42]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Discussion:
This message is a reminder that Fedora Linux 42 is nearing its end of life.
Fedora will stop maintaining and issuing updates for Fedora Linux 42 on 2026-05-13.
It is Fedora's policy to close all bug reports from releases that are no longer
maintained. At that time this bug will be closed as EOL if it remains open with a
'version' of '42'.
Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, change the 'version'
to a later Fed
Bugzilla
CVE-2026-21637 nodejs: Nodejs denial of service
bugzilla·2026-01-20·CVSS 7.5
CVE-2026-21637 [HIGH] CVE-2026-21637 nodejs: Nodejs denial of service
CVE-2026-21637 nodejs: Nodejs denial of service
A flaw in Node.js TLS error handling allows remote attackers to crash or exhaust resources of a TLS server when `pskCallback` or `ALPNCallback` are in use. Synchronous exceptions thrown during these callbacks bypass standard TLS error handling paths (tlsClientError and error), causing either immediate process termination or silent file descriptor leaks that eventually lead to denial of service. Because these callbacks process attacker-controlled input during the TLS handshake, a remote client can repeatedly trigger the issue. This vulnerability affects TLS servers using PSK or ALPN callbacks across Node.js versions where these callbacks throw without being safely wrapped.
Discussion:
This issue has been addressed in the following products:
Hackernews
Microsoft Issues Patches for SharePoint Zero-Day and 168 Other New Vulnerabilities
blogs_hackernews·2026-04-15·CVSS 7.5
[HIGH] Microsoft Issues Patches for SharePoint Zero-Day and 168 Other New Vulnerabilities
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## Microsoft Issues Patches for SharePoint Zero-Day and 168 Other New Vulnerabilities
Microsoft on Tuesday released updates to address a record 169 security flaws across its product portfolio, including one vulnerability that has been actively exploited in the wild.
Of these 169 vulnerabilities, 157 are rated Important, eight are rated Critical, three are rated Moderate, and one is rated Low in severity. Ninety-three of the flaws are classified as privilege escalation, followed by 21 information disclosure, 21 remote code execution, 14 security feature bypass, 10 spoofing, and nine denial-of-service vulnerabilities.
Also inclu
Bleepingcomputer
Microsoft April 2026 Patch Tuesday fixes 167 flaws, 2 zero-days
blogs_bleepingcomputer·2026-04-14·CVSS 6.5
[MEDIUM] Microsoft April 2026 Patch Tuesday fixes 167 flaws, 2 zero-days
## Microsoft April 2026 Patch Tuesday fixes 167 flaws, 2 zero-days
## Lawrence Abrams
Today is Microsoft's April 2026 Patch Tuesday with security updates for 167 flaws, including 2 zero-day vulnerabilities.
This Patch Tuesday also addresses eight "Critical" vulnerabilities, 7 of which are remote code execution flaws and the other is a denial of service flaw.
The number of bugs in each vulnerability category is listed below:
93 Elevation of Privilege Vulnerabilities
13 Security Feature Bypass Vulnerabilities
20 Remote Code Execution Vulnerabilities
21 Information Disclosure Vulnerabilities
10 Denial of Service Vulnerabilities
9 Spoofing Vulnerabilities
When BleepingComputer reports on Patch Tuesday security updates, we only count those released by Microsoft today.
Therefore, the
Rapid7
Patch Tuesday - April 2026
blogs_rapid7·2026-04-14·CVSS 6.5
[MEDIUM] Patch Tuesday - April 2026
Microsoft is publishing 167 vulnerabilities on April 2026 Patch Tuesday . Microsoft is aware of exploitation in the wild for one of today’s vulnerabilities, and public disclosure for one other. Microsoft evaluates 19 of the vulnerabilities published today as more likely to see future exploitation. So far this month, Microsoft has provided patches to address 80 browser vulnerabilities, which are not included in the Patch Tuesday count above.
## Increasing volumes of vulnerabilities
Regular Patch Tuesday watchers will know that these vulnerability totals are significantly higher than usual, especially the browser numbers. Late last week, Microsoft published patches to resolve more than 60 browser vulnerabilities in a single day, which is a new record in that very specific category.
It mig
Hackernews
⚡ Weekly Recap: Telecom Sleeper Cells, LLM Jailbreaks, Apple Forces U.K. Age Checks and More
blogs_hackernews·2026-03-30·CVSS 9.3
[CRITICAL] ⚡ Weekly Recap: Telecom Sleeper Cells, LLM Jailbreaks, Apple Forces U.K. Age Checks and More
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## ⚡ Weekly Recap: Telecom Sleeper Cells, LLM Jailbreaks, Apple Forces U.K. Age Checks and More
Some weeks are loud. This one was quieter but not in a good way. Long-running operations are finally hitting courtrooms, old attack methods are showing up in new places, and research that stopped being theoretical right around the time defenders stopped paying attention.
There's a bit of everything this week. Persistence plays, legal wins, influence ops, and at least one thing that looks boring until you see what it connects to.
All of it below. Let's go.
## ⚡ Threat of the Week
Citrix Flaw Comes Under Active Exploitation — A cr
Wiz
CVE-2026-21637 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-21637 [HIGH] CVE-2026-21637 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-21637 :
npm vulnerability analysis and mitigation
pskCallback
ALPNCallback
Source : NVD
## 7.5
Score
Published January 20, 2026
Severity HIGH
CNA Score 5.9
Affected Technologies
npm
Node.js
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 13.6
Exploitation Probability (EPSS) N/A
Affected packages and libraries
nodejs-docs
nodejs:24::nodejs-libs
Sources
AlmaLinux 8 Severity HIGH Has Fix Added at: Feb 15, 2026
AlmaLinux 9 Severity HIGH Has Fix Added at: Feb 19, 2026
Alpine 3.21 Severity HIGH Has Fix Added at: Apr 06, 2026
Alpine 3.22 Severity HIGH Has Fix Added at: Jan 23, 2026
Alpine 3.23, edge Severity HIGH Has Fix Added at: Jan 18, 2026
CBL-Mariner 3.0 Severity
2026-01-20
Published