CVE-2026-16001 (GCVE-0-2026-16001)
Vulnerability from cvelistv5
Published
2026-10-02 06:55
Modified
2026-10-02 17:55
Severity ?
VLAI Severity ?
EPSS score ?
CWE
- CWE-354 - Improper Validation of Integrity Check Value
Summary
Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was taken from the key derivation output directly after a keystream as long as the message, while the derivation input depends only on the static key pair and fixed parameters. The keystream revealed by that one message therefore contains the MAC key for every sufficiently shorter message.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Legion of the Bouncy Castle Inc. | bc-csharp |
Version: 0 ≤ |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-16001",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-02T17:54:38.625547Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-10-02T17:55:04.562Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography",
"defaultStatus": "unaffected",
"packageName": "BouncyCastle.Cryptography",
"product": "bc-csharp",
"programFiles": [
"crypto/src/crypto/engines/IesEngine.cs"
],
"repo": "https://github.com/bcgit/bc-csharp",
"vendor": "Legion of the Bouncy Castle Inc.",
"versions": [
{
"lessThan": "2.7.0",
"status": "affected",
"version": "0",
"versionType": "semver"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Discovered by Claude, Anthropic\u0027s AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research."
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was taken from the key derivation output directly after a keystream as long as the message, while the derivation input depends only on the static key pair and fixed parameters. The keystream revealed by that one message therefore contains the MAC key for every sufficiently shorter message."
}
],
"value": "Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was taken from the key derivation output directly after a keystream as long as the message, while the derivation input depends only on the static key pair and fixed parameters. The keystream revealed by that one message therefore contains the MAC key for every sufficiently shorter message."
}
],
"impacts": [
{
"descriptions": [
{
"lang": "en",
"value": "Integrity: forgery of authenticated stream-mode IES messages from one known-plaintext observation"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 8.2,
"baseSeverity": "HIGH",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-354",
"description": "CWE-354 Improper Validation of Integrity Check Value",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-02T06:55:36.057Z",
"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630",
"shortName": "bcorg"
},
"references": [
{
"tags": [
"vendor-advisory"
],
"url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001"
},
{
"tags": [
"patch"
],
"url": "https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "IesEngine stream-mode MAC forgery via length-dependent KDF split",
"x_antReportIds": [
"ANT-2026-WZ2GJBGD"
],
"x_generator": {
"engine": "Claude Opus 5.5"
}
}
},
"cveMetadata": {
"assignerOrgId": "91579145-5d7b-4cc5-b925-a0262ff19630",
"assignerShortName": "bcorg",
"cveId": "CVE-2026-16001",
"datePublished": "2026-10-02T06:55:36.057Z",
"dateReserved": "2026-07-16T23:53:44.147Z",
"dateUpdated": "2026-10-02T17:55:04.562Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"vulnrichment": {
"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-16001\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-10-02T17:54:38.625547Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-10-02T17:54:56.003Z\"}}], \"cna\": {\"title\": \"IesEngine stream-mode MAC forgery via length-dependent KDF split\", \"source\": {\"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Discovered by Claude, Anthropic\u0027s AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research.\"}], \"impacts\": [{\"descriptions\": [{\"lang\": \"en\", \"value\": \"Integrity: forgery of authenticated stream-mode IES messages from one known-plaintext observation\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 8.2, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N\", \"exploitMaturity\": \"NOT_DEFINED\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"HIGH\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"repo\": \"https://github.com/bcgit/bc-csharp\", \"vendor\": \"Legion of the Bouncy Castle Inc.\", \"product\": \"bc-csharp\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"2.7.0\", \"versionType\": \"semver\"}], \"packageName\": \"BouncyCastle.Cryptography\", \"programFiles\": [\"crypto/src/crypto/engines/IesEngine.cs\"], \"collectionURL\": \"https://www.nuget.org/packages/BouncyCastle.Cryptography\", \"defaultStatus\": \"unaffected\"}], \"references\": [{\"url\": \"https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16001\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d\", \"tags\": [\"patch\"]}], \"x_generator\": {\"engine\": \"Claude Opus 5.5\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was taken from the key derivation output directly after a keystream as long as the message, while the derivation input depends only on the static key pair and fixed parameters. The keystream revealed by that one message therefore contains the MAC key for every sufficiently shorter message.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was taken from the key derivation output directly after a keystream as long as the message, while the derivation input depends only on the static key pair and fixed parameters. The keystream revealed by that one message therefore contains the MAC key for every sufficiently shorter message.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-354\", \"description\": \"CWE-354 Improper Validation of Integrity Check Value\"}]}], \"x_antReportIds\": [\"ANT-2026-WZ2GJBGD\"], \"providerMetadata\": {\"orgId\": \"91579145-5d7b-4cc5-b925-a0262ff19630\", \"shortName\": \"bcorg\", \"dateUpdated\": \"2026-10-02T06:55:36.057Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-16001\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-10-02T17:55:04.562Z\", \"dateReserved\": \"2026-07-16T23:53:44.147Z\", \"assignerOrgId\": \"91579145-5d7b-4cc5-b925-a0262ff19630\", \"datePublished\": \"2026-10-02T06:55:36.057Z\", \"assignerShortName\": \"bcorg\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
Loading…
Loading…