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GHSA-jm5c-rv3w-w83m CVE-2020-26242 GO-2021-0103

Denial of service in geth

Medium Go
Severity
6.5 / 10
Medium · CVSS 3.1
Exploit chance (EPSS)
1.48%
Chance of exploitation in the next 30 days. Higher than 73.92% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-125 Out-of-bounds Read
CWE-191 Integer Underflow (Wrap or Wraparound)
CWE-400 Uncontrolled Resource Consumption
Fix
Available
2 packages have a fixed version

Description

Impact

Denial-of-service (crash) during block processing

Details

Affected versions suffer from a vulnerability which can be exploited through the MULMOD operation, by specifying a modulo of 0: mulmod(a,b,0), causing a panic in the underlying library. The crash was in the uint256 library, where a buffer underflowed.

if `d == 0`, `dLen` remains `0`

and https://github.com/holiman/uint256/blob/4ce82e695c10ddad57215bdbeafb68b8c5df2c30/uint256.go#L451 will try to access index [-1].

The uint256 library was first merged in this commit, on 2020-06-08. Exploiting this vulnerabilty would cause all vulnerable nodes to drop off the network.

The issue was brought to our attention through a bug report, showing a panic occurring on sync from genesis on the Ropsten network.

It was estimated that the least obvious way to fix this would be to merge the fix into uint256, make a new release of that library and then update the geth-dependency.

Patches

Upgrade to v1.9.18 or higher

Workarounds

Not at this time

References

https://blog.ethereum.org/2020/11/12/geth_security_release/

For more information

If you have any questions or comments about this advisory:

Affected versions

Go

PackageVulnerableFixed in
github.com/ethereum/go-ethereum
>= 1.9.16, < 1.9.18
1.9.18
github.com/holiman/uint256
>= 0.1.0, < 1.1.1
1.1.1

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

github.com/ethereum/go-ethereum Go → 1.9.18

go
go get github.com/ethereum/go-ethereum@v1.9.18 && go mod tidy

github.com/holiman/uint256 Go → 1.1.1

go
go get github.com/holiman/uint256@v1.1.1 && go mod tidy

Severity breakdown

CVSS 3.1 6.5

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Weakness

CWE-125: Out-of-bounds Read

The product reads data past the end, or before the beginning, of the intended buffer.

How to prevent it
  • Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.
  • Architecture and Design: Use a language that provides appropriate memory abstractions.

CWE-191: Integer Underflow (Wrap or Wraparound)

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

CWE-400: Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.

How to prevent it
  • Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
  • Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
  • Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
  • Implementation: Ensure that all failures in resource allocation place the system into a safe posture.

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-m6j8-rg6r-7mv8
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High Also affects github.com/ethereum/go-ethereum
GHSA-2gjw-fg97-vg3r
Go Ethereum affected by DoS via malicious p2p message
High Also affects github.com/ethereum/go-ethereum
GHSA-689v-6xwf-5jf3
Go Ethereum affected by DoS via malicious p2p message
High Also affects github.com/ethereum/go-ethereum
GHSA-mq3p-rrmp-79jg
go-ethereum is vulnerable to high CPU usage leading to DoS via malicious p2p message
High Also affects github.com/ethereum/go-ethereum
GHSA-mr7q-c9w9-wh4h
go-ethereum is vulnerable to DoS via malicious p2p message affecting a vulnerable node
High Also affects github.com/ethereum/go-ethereum
GHSA-q26p-9cq4-7fc2
Go Ethereum vulnerable to DoS via malicious p2p message
Medium Also affects github.com/ethereum/go-ethereum
GHSA-4xc9-8hmq-j652
go-ethereum vulnerable to DoS via malicious p2p message
High Also affects github.com/ethereum/go-ethereum
GHSA-v9jh-j8px-98vq
go-ethereum vulnerable to denial of service via crafted GraphQL query
High Also affects github.com/ethereum/go-ethereum

Credits: Dima Stebaev

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