CVE-2023-6245 | Infinite decoding loop through specially crafted payload

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.

Published: 2023-12-08 Last update: 2024-11-21 Assigner: 6b35d637-e00f-4228-858c-b20ad6e1d07b Source: 6b35d637-e00f-4228-858c-b20ad6e1d07b
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-6245 is rated Moderate Risk (40.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.13%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-6245

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.96% 0.13% -0.83%
2 2025-11-18 0.13% 0.96% +0.83%
3 2025-04-15 — 0.13% —

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-6245

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 6b35d637-e00f-4228-858c-b20ad6e1d07b
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2023-6245

GitHub Security Advisory for CVE-2023-6245

GHSA-7787-p7x6-fq3j · Severity: high · Ecosystem: rust — Candid infinite decoding loop through specially crafted payload

OS Trackers for CVE-2023-6245

vendor priority summary link
ubuntu medium CVE-2023-6245 medium priority: Ubuntu including 1 source packages (candid), 12 status rows across 12 suites (bionic, focal, jammy, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 8, ignored 2, not-affected 1, released 1. https://ubuntu.com/security/CVE-2023-6245

Affected software / configurations for CVE-2023-6245

Vendor Product Version Raw CPE
dfinity candid >= 0.9.0, < 0.9.10 cpe:2.3:a:dfinity:candid:*:*:*:*:*:rust:*:*

References for CVE-2023-6245

cvelogic Threat Intelligence