GHSA-8gjm-h3xj-mp6w CVE-2021-45698 GHSA-v666-6w97-pcwm RUSTSEC-2021-0107

RPC call failure in ckb

Critical crates.io

Severity: 9.8 / 10; Critical · CVSS 3.1
Exploit chance (EPSS): 1.23%; Chance of exploitation in the next 30 days. Higher than 68.95% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
Fix: 0.40.0; Upgrade ckb to this version or later

Description

An issue was discovered in the ckb crate before 0.40.0 for Rust. A get_block_template RPC call may fail in situations where it is supposed to select a Nervos CKB blockchain transaction with a higher fee rate than another transaction.

Affected versions

crates.io

Package	Vulnerable	Fixed in
ckb	`< 0.40.0`	`0.40.0`
ckb	`>= 0.0.0-0, < 0.40.0`	`0.40.0`

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.

ckb crates.io → `0.40.0`

cargo

cargo update -p ckb --precise 0.40.0

Severity breakdown

CVSS 3.1 9.8

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

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

Weakness

CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.

How to prevent it

Implementation: The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
Implementation: When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
Architecture and Design: Limit the interleaving of operations on files from multiple processes.
Implementation, Architecture and Design: If you cannot perform operations atomically and you must share access to the resource between multiple processes or threads, then try to limit the amount of time (CPU cycles) between the check and use of the resource. This will not fix the problem, but it could make it more difficult for an attack to succeed.
Implementation: Recheck the resource after the use call to verify that the action was taken appropriately.
Architecture and Design: Ensure that some environmental locking mechanism can be used to protect resources effectively.
Implementation: Ensure that locking occurs before the check, as opposed to afterwards, such that the resource, as checked, is the same as it is when in use.

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2021-45698

Packages

Timeline

Jul 25, 2021 Published
Oct 12, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-29c2-65rj-h343 Nervos CKB Permit load cell data from memory	Medium	Also affects ckb
GHSA-h4c3-5275-vrmg Nervos CKB Pool does not remove the conflicting transactions from the statistics	Medium	Also affects ckb
GHSA-q73f-w3h7-7wcc Nervos CKB Transaction which calls syscall load_cell_data_hash has nondeterministic result	Critical	Also affects ckb
GHSA-3gjh-29fv-8hr6 Nervos CKB Snappy decompress length can be very large and causes out of memory error	High	Also affects ckb
GHSA-wjxc-pjx9-4wvm Nervos CKB Panic on malformed input	High	Also affects ckb
GHSA-hjqq-29pw-96wj Nervos CKB node panics when processing a block which parent timestamp is too new	High	Also affects ckb
GHSA-r9rv-9mh8-pxf4 Nervos CKB BlockTimeTooNew should not be considered as invalid block	Medium	Also affects ckb
GHSA-pr39-8257-fxc2 Nervos CKB DoS: Process exists when p2p discovery protocol receives unsupported peer IP	Low	Also affects ckb

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