crypto/tls: Asymmetric Resource Consumption (Amplification)
CVE-2026-97031 is a high-severity asymmetric resource consumption (amplification) vulnerability in crypto/tls from Go standard library, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 1.26.9, 1.27.2 as the first without the flaw, so updating crypto/tls to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.72% chance of exploitation within 30 days, higher than 54% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update crypto/tls to 1.26.9 or 1.27.2, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Go standard library | crypto/tls | before 1.26.9; 1.27.0-0 up to, but not including, 1.27.2 | 1.26.9, 1.27.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CISA (ADP).
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Asymmetric Resource Consumption (Amplification)
The product does not properly control situations in which an adversary can cause the product to consume or produce excessive resources without requiring the adversary to invest equivalent work or otherwise prove authorization, i.e., the adversary's influence is asymmetric.
How developers prevent this class of flaw
- An application must make resources available to a client commensurate with the client's access level.
- An application must, at all times, keep track of allocated resources and meter their usage appropriately.
- Consider disabling resource-intensive algorithms on the server side, such as Diffie-Hellman key exchange.
More Asymmetric Resource Consumption (Amplification) vulnerabilities (CWE-405)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in crypto/tls
- 7.5 High severity
- 7.5 High severity
- 10.0 Critical severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent Asymmetric Resource Consumption (Amplification) vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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