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GHSA-fmm9-3gv8-58f4
No affected components available
Impact
Attackers that could provide arbitrary YAML input to an application that uses kaml could cause the application to endlessly loop while parsing the input. This could result in resource starvation and denial of service.
This only affects applications that use polymorphic serialization with the default tagged polymorphism style. Applications using the property polymorphism style are not affected.
YAML input for a polymorphic type that provided a tag but no value for the object would trigger the issue, for example:
!<x>
The following is a sample application that demonstrates this issue:
import com.charleskorn.kaml.Yaml
import kotlinx.serialization.SerialName
import kotlinx.serialization.Serializable
@Serializable
private sealed class K {
@Serializable
@SerialName("x")
data class X(
val property: String? = null,
) : K()
}
const val s = """
!<x>
"""
fun main() {
println("Started.")
val result = Yaml.default.decodeFromString(K.serializer(), s)
println("Finished, result is $result")
}
On vulnerable versions of kaml, the decodeFromString() operation hangs and never returns.
Patches
Version 0.35.3 or later contain the fix for this issue.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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