Reject malformed ECH outer extension references in crypto/tls
Noroxi assessment
Priority: Monitor (action score 30/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.39% (FIRST EPSS).
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- Fixed version: Go standard library crypto/tls 1.26.9, 1.27.2; azl3 golang 1.26.7-1 on Azure Linux 3.0 Release Notes; azl3 golang 1.27.1-1 on Azure Linux 3.0 Release Notes.
Low priority for now. Upgrade to Go standard library crypto/tls 1.26.9, 1.27.2; azl3 golang 1.26.7-1 on Azure Linux 3.0 Release Notes; azl3 golang 1.27.1-1 on Azure Linux 3.0 Release Notes or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
Multiple ECH outer extension references are not permitted under RFC 9849; previously, a client could send a well-crafted packet that could trigger memory exhaustion in the server process by specifying multiple references. We now reject these as malformed and curb the memory amplification vector as a result.
- Published
- Oct 8, 2026
- Updated
- Oct 9, 2026
- EPSS
- 0.3% · 32th percentile
- CWE
- CWE-405
Report tools
Action score
30
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Go). Independent of NVD's CPE analysis and usually ahead of it.
Go standard library crypto/tls
- before 1.26.9affected · semver
- 1.27.0-0 and later · before 1.27.2affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | golang-1.19 | from 0 | — |
| Debian:13 | golang-1.24 | from 0 | — |
| Debian:14 | golang-1.26 | before 1.26.9-1 | 1.26.9-1 |
| Debian:14 | golang-1.27 | before 1.27.2-1 | 1.27.2-1 |
| Go | stdlib | from 1.27.0-0 · before 1.27.2 | 1.27.2 |
| Go | stdlib | before 1.26.9 | 1.26.9 |
| openSUSE:Leap 16.0 | go1.26 | before 1.26.9-160000.1.1 | 1.26.9-160000.1.1 |
| openSUSE:Leap 16.0 | go1.27 | before 1.27.2-160000.1.1 | 1.27.2-160000.1.1 |
| openSUSE:Tumbleweed | go1.26 | before 1.26.9-1.1 | 1.26.9-1.1 |
| openSUSE:Tumbleweed | go1.27 | before 1.27.2-1.1 | 1.27.2-1.1 |
| openSUSE:Tumbleweed | rclone | before 1.75.2-1.1 | 1.75.2-1.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP7 | go1.26 | before 1.26.9-150000.1.33.1 | 1.26.9-150000.1.33.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP7 | go1.27 | before 1.27.2-150000.1.12.1 | 1.27.2-150000.1.12.1 |
Same product
go standard library: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-56862Limit handshake messages we are willing to accept post-handshake in crypto/tls30Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Go standard library crypto/tls | 1.26.9 | Vendor (CNA) |
| Go standard library crypto/tls | 1.27.2 | Vendor (CNA) |
| azl3 golang 1.26.7-1 on Azure Linux 3.0 | Release Notes | Microsoft (MSRC) |
| azl3 golang 1.27.1-1 on Azure Linux 3.0 | Release Notes | Microsoft (MSRC) |
| debian:golang-1.26 | 1.26.9-1 · Debian:14 | Package registry (OSV) |
| debian:golang-1.27 | 1.27.2-1 · Debian:14 | Package registry (OSV) |
| Go:stdlib | 1.26.9 | Package registry (OSV) |
| Go:stdlib | 1.27.2 | Package registry (OSV) |
| opensuse:go1.26 | 1.26.9-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| opensuse:go1.27 | 1.27.2-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| opensuse:rclone | 1.75.2-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| suse:go1.26 | 1.26.9-150000.1.33.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7 | Package registry (OSV) |
| suse:go1.27 | 1.27.2-150000.1.12.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- Published
- Fix recordedsame day
- TodayOct 20, 2026+12 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-405 · Asymmetric Resource Consumption (Amplification)CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- CVSS— → 7.5
- Severity— → high
- SSVC exploitation— → none
- Exploit maturity— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (3 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.