CVE-2026-123611
rustls before 0.23.46 Key Exchange Downgrade via Unauthenticated ServerHello
Description
rustls before 0.23.46 contains a key exchange downgrade vulnerability that allows network attackers to poison the per-server-name key-exchange group record via an unauthenticated ServerHello. Attackers can answer one connection with a ServerHello selecting X25519, causing later ClientHellos to send only classical shares and lose post-quantum confidentiality.
INFO
Published Date :
Nov. 8, 2026, 2:16 a.m.
Last Modified :
Nov. 8, 2026, 2:16 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | LOW | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | LOW | MITRE-CVE | ||||
| CVSS 3.1 | LOW | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update rustls to version 0.23.46 or later.
- Ensure post-quantum confidentiality is maintained.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-123611.
| URL | Resource |
|---|---|
| https://github.com/rustls/rustls/security/advisories/GHSA-w44r-93j7-qv28 | |
| https://www.vulncheck.com/advisories/rustls-before-0.23.46-key-exchange-downgrade-via-unauthenticated-serverhello |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-123611 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-123611
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-123611 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-123611 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Nov. 08, 2026
Action Type Old Value New Value Added Description rustls before 0.23.46 contains a key exchange downgrade vulnerability that allows network attackers to poison the per-server-name key-exchange group record via an unauthenticated ServerHello. Attackers can answer one connection with a ServerHello selecting X25519, causing later ClientHellos to send only classical shares and lose post-quantum confidentiality. Added CVSS V4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N Added CWE CWE-757 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/123xxx/CVE-2026-123611.json">CVE-2026-123611</a> Added Reference https://github.com/rustls/rustls/security/advisories/GHSA-w44r-93j7-qv28 Added Reference https://www.vulncheck.com/advisories/rustls-before-0.23.46-key-exchange-downgrade-via-unauthenticated-serverhello