Critical Cryptography exploit reference

CVE-2026-44726 — Deno Node.js TLS Compatibility Layer Cleartext Transmission After Connection Retry (CWE-319)

Deno is a JavaScript, TypeScript, and WebAssembly runtime. From 2.0.0 until 2.7.8, a flaw in Deno's Node.js tls compatibility layer could cause a TLS client to transmit application data in plaintext after a connection retry. When `autoSelectFamily was enabled and the first address-family attempt failed, the socket reinitialization path reused a stale TLS upgrade hook that was bound to the original, failed handle. As a result, the replacement TCP connection was never upgraded to TLS, and any data the application wrote before the secureConnect event travelled over the network unencrypted. A network attacker positioned to cause the initial connection attempt to fail (for example, by dropping IPv6 traffic on a dual-stack host) could deterministically trigger the fallback path and observe or tamper with traffic that the application believed was TLS-protected. This vulnerability is fixed in 2.7.8.

Published Jun 23, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+2
Technical severity (critical)+10

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.23%

ahead of 13% of scored CVEs · Oct 14, 2026

Affects

Deno

CVSS base

9.1

Critical · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Deno Deno, Denoland Deno).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Deno	Deno	≥ 2.0.0 and < 2.7.8	Vulnerable	NIST National Vulnerability Database
Denoland	Deno	version >= 2.0.0, < 2.7.8	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.1	CVSS 3.1	Critical	3.9	5.2	nvd@nist.gov via NIST National Vulnerability Database
7.4	CVSS 3.1	High	2.2	5.2	security-advisories@github.com via NIST National Vulnerability Database
7.4	CVSS 3.1	High	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N (score shown at the top: nvd@nist.gov)

Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 9.1 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-319 · Cleartext Transmission of Sensitive Information

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.23%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Check TLS negotiations and unexpected certificates in the component’s traffic.

web/proxy/WAF logsnetwork IDS/IPS

Analysis and videos

CVE-2026-44726: Deno Node.js TLS Compatibility Layer Cleartext Transmission After Connection Retry (CWE-319)
Deno versions from 2.0.0 before 2.7.8 can send application data without encryption when a TLS client falls back to another address family after a failed first attempt. The flaw is tied to the autoSelectFamily behavior in Deno's Node.js tls compatibility layer and is stated to be fixed in 2.7.8. NVD scores it 9.1 under CVSS 3.1, and no confirmed exploitation appears in the sources consulted.

Timeline

What happened to this CVE, newest first.

2026
Affected products added · denoland/deno
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 9.1
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Jun 23, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

github.com/denoland/deno/security/advisories/GHSA-chqv-56wv-7564
Exploit, Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

Deno
every CVE for this vendor

Cryptography
same class

CWE-319
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-55517 Deno: Denial of service via non-ASCII bytes in WebSocket response headers Jun 23, 2026
Medium CVE-2026-49860 Deno: WebSocket API sandbox bypass via missing post-DNS check Jun 23, 2026
Medium CVE-2026-49983 Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access Jun 23, 2026
High CVE-2026-49402 Deno: Command Injection via spawnSync & spawn on Windows Jun 23, 2026
Medium CVE-2026-49411 Deno Node TCPWrap numeric hostname aliases bypass --deny-net resolved-IP deny checks Jun 23, 2026
Medium CVE-2026-49406 Deno: BYONM module resolution allows `package.json` main path traversal to bypass `--allow-read` restrictions Jun 23, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-44726 is "Deno Node.js TLS Compatibility Layer Cleartext Transmission After Connection Retry (CWE-319)", rated Critical. It affects Deno (Deno); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.1 describes technical severity. EPSS 0.23% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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