CVE-2026-71892
08h30 +00:00
CVE 설명
CMS key-transport recipient key-size validation never runs for RFC 9709 HKDF-derived keys
In Bouncy Castle for Java before 1.86, the opt-in key-size validation on CMS key-transport recipients, org.bouncycastle.cms.jcajce.JceKeyTransRecipient.setKeySizeValidation(true), never ran for a message using RFC 9709 content-encryption key derivation (id-alg-cek-hkdf-sha256). The branch that should have selected the actual content-encryption algorithm carried in the key derivation AlgorithmIdentifier's parameters compared the encrypted-key byte array against the id-alg-cek-hkdf-sha256 object identifier, a comparison between a byte array and an ASN1ObjectIdentifier that is false for every possible input, so the check fell through to a key-size lookup on the outer wrapper OID. That OID identifies a key-derivation construction rather than a cipher and has no registered key size, so the size comparison was skipped entirely. A key-transport EnvelopedData or AuthEnvelopedData whose transported, HKDF-derived content-encryption key did not match the key size of the advertised content-encryption algorithm was therefore accepted even with validation explicitly enabled, silently defeating the only mechanism the API offers for enforcing recovered key size. The recipient now dispatches on the content-encryption AlgorithmIdentifier's algorithm OID, so validation checks the recovered key against the inner content-encryption algorithm. Messages with a matching key size, non-HKDF messages, and recipients that do not enable validation are unaffected. This issue also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).CVE 정보
관련 약점
| 약점 이름 | 출처 | |
|---|---|---|
| Incorrect Comparison The product compares two entities in a security-relevant context, but the comparison is incorrect. |
메트릭
| 메트릭 | 점수 | 심각도 | CVSS 벡터 | 출처 |
|---|---|---|---|---|
| V4.0 | 6.9 | MEDIUM |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/U:Amber
추가 정보
Base: Exploitabilty MetricsThe Exploitability metrics reflect the characteristics of the “thing that is vulnerable”, which we refer to formally as the vulnerable system. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. Network The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). Attack Complexity This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. Low The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system. Attack Requirements This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. None The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability. Privileges Required This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. None The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack. User Interaction This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. None The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges Base: Impact MetricsThe Impact metrics capture the effects of a successfully exploited vulnerability. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve. Confidentiality Impact This metric measures the impact to the confidentiality of the information managed by the system due to a successfully exploited vulnerability. Low There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Low Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System. Availability Impact This metric measures the impact to the availability of the impacted system resulting from a successfully exploited vulnerability. None There is no impact to availability within the Vulnerable System. Sub Confidentiality Impact Negligible There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System. Sub Integrity Impact None There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System. Sub Availability Impact None There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System. Threat MetricsThe Threat metrics measure the current state of exploit techniques or code availability for a vulnerability. Environmental MetricsThese metrics enable the consumer analyst to customize the resulting score depending on the importance of the affected IT asset to a user’s organization, measured in terms of complementary/alternative security controls in place, Confidentiality, Integrity, and Availability. The metrics are the modified equivalent of Base metrics and are assigned values based on the system placement within organizational infrastructure. Supplemental MetricsSupplemental metric group provides new metrics that describe and measure additional extrinsic attributes of a vulnerability. While the assessment of Supplemental metrics is provisioned by the provider, the usage and response plan of each metric within the Supplemental metric group is determined by the consumer. Provider Urgency Many vendors currently provide supplemental severity ratings to consumers via product security advisories. Amber Provider has assessed the impact of this vulnerability as having a moderate urgency. |
