CVE-2023-6245
highpriority · track · 30EPSS 0.012 · 68 %ileEUUSEPSS · scored 2026-10-27
The Candid library causes a Denial of Service while parsing a specially crafted payload with 'empty' data type. For example, if the payload is `record { * ; empty }` and the canister interface expects `record { * }` then the Rust candid decoder treats empty as an extra field required by the type. The problem with the type empty is that the candid Rust library wrongly categorizes empty as a recoverable error when skipping the field and thus causing an infinite decoding loop. Canisters using affected versions of candid are exposed to denial of service by causing the decoding to run indefinitely until the canister traps due to reaching maximum instruction limit per execution round. Repeated exposure to the payload will result in degraded performance of the canister. Note: Canisters written in Motoko are unaffected.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.9–7.5
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (3)
Products and version ranges known to be affected.
advisories (2)
Vendor and ecosystem advisories describing this.
- GHSA-7787-p7x6-fq3jCandid infinite decoding loop through specially crafted payload2023-12-08ghsa · osvUS
### Impact The Candid library causes a Denial of Service while parsing a specially crafted payload with `empty` data type. For example, if the payload is `record { * ; empty }` and the canister interface expects `record { * }` then the rust candid decoder treats `empty` as an extra field required by the type. The problem with type `empty` is that the candid rust library wrongly categorizes `empty` as a recoverable error when skipping the field and thus causing an infinite decoding loop. Canisters using affected versions of candid are exposed to denial of service by causing the decoding to run indefinitely until the canister traps due to reaching maximum instruction limit per execution round. Repeated exposure to the payload will result in degraded performance of the canister. For asset canister users, `dfx` versions `>= 0.14.4` to `<= 0.15.2-beta.0` ships asset canister with an affected version of candid. #### Unaffected - Rust canisters using candid `< 0.9.0` or `>= 0.9.10` - Rust canister interfaces of type other than `record { * }` - Motoko based canisters - dfx (for asset canister) `<= 0.14.3` or `>= 0.15.2` ### Patches The issue has been patched in `0.9.10`. All rust based canisters on candid versions `>= 0.9.0` must upgrade their candid versions to `>= 0.9.10` and deploy their canisters to mainnet as soon as possible. ### Workarounds There is no workaround for canisters using the affected versions of candid other than upgrading to patched version. ### References - [dfinity/candid/pull/478](https://github.com/dfinity/candid/pull/478) - [Candid Library Reference](https://internetcomputer.org/docs/current/references/candid-ref) - [Candid Specification](https://github.com/dfinity/candid/blob/master/spec/Candid.md) - [Internet Computer Specification](https://internetcomputer.org/docs/current/references/ic-interface-spec)
- RUSTSEC-2023-0073Infinite decoding loop through specially crafted payload2023-12-08vendor · osvUS
The Candid library causes a Denial of Service while parsing a specially crafted payload with `empty` data type. For example, if the payload is `record { * ; empty }` and the canister interface expects `record { * }` then the rust candid decoder treats `empty` as an extra field required by the type. The problem with type `empty` is that the candid rust library wrongly categorizes `empty` as a recoverable error when skipping the field and thus causing an infinite decoding loop. Canisters using affected versions of candid are exposed to denial of service by causing the decoding to run indefinitely until the canister traps due to reaching maximum instruction limit per execution round. Repeated exposure to the payload will result in degraded performance of the canister. For asset canister users, `dfx` versions `>= 0.14.4` to `<= 0.15.2-beta.0` ships asset canister with an affected version of candid. ### Unaffected - Rust canisters using candid `< 0.9.0` or `>= 0.9.10` - Rust canister interfaces of type other than `record { * }` - Motoko based canisters - dfx (for asset canister) `<= 0.14.3` or `>= 0.15.2` ### References - [GitHub Security Advisory (GHSA-7787-p7x6-fq3j)](https://github.com/dfinity/candid/security/advisories/GHSA-7787-p7x6-fq3j) - [dfinity/candid/pull/478](https://github.com/dfinity/candid/pull/478) - [Candid Library Reference](https://internetcomputer.org/docs/current/references/candid-ref) - [Candid Specification](https://github.com/dfinity/candid/blob/master/spec/Candid.md) - [Internet Computer Specification](https://internetcomputer.org/docs/current/references/ic-interface-spec)
also known as (5)
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sources
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references (16)
External citations — patches, advisories, analysis.
- https://cxsecurity.com/cveshow/CVE-2023-6245/cnnvd
- https://github.com/dfinity/candid/blob/master/spec/Candid.mdcnnvd
- https://github.com/dfinity/candid/pull/478cnnvd
- https://github.com/dfinity/candid/security/advisories/GHSA-7787-p7x6-fq3jcnnvd
- https://internetcomputer.org/docs/current/references/candid-refcnnvd
- https://internetcomputer.org/docs/current/references/ic-interface-speccnnvd
- https://github.com/dfinity/candid/blob/master/spec/Candid.mdenisa_euvd
- https://github.com/dfinity/candid/pull/478enisa_euvd
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