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CVE-2026-103601— CcmBlockCipher and KCcmBlockCipher leave unverified plaintext in the output buffer after a failed tag check

Quick assessment

Affected
Legion of the Bouncy Castle Inc. bc-csharp
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Bouncy Castle Inc. 的 bc-csharp 库（版本低于 2.7.0）中，CCM（CcmBlockCipher）和 DSTU 7624 CCM（KCcmBlockCipher）AEAD 模式存在未经验证的明文释放漏洞。远程攻击者可通过向应用发送伪造消息，并观察失败解密操作的输出缓冲区（例如通过缓冲区重用或日志记录），从而获取其对任意密文进行解密的结果。 该漏洞的根本原因在于：在验证认证标签之前，解密操作已将恢复出的明文写入调用方提供的输出缓冲区；当后续认证检查失败时，该明文仍保留在缓冲区中未被

CVSS 8.2 · High EPSS 0.29% · P19

Affected Version Matrix 1

VendorProduct Version RangeStatus
Legion of the Bouncy Castle Inc. bc-csharp < 2.7.0 affected
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I. Basic Information for CVE-2026-103601

Vulnerability Information
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Vulnerability Title
CcmBlockCipher and KCcmBlockCipher leave unverified plaintext in the output buffer after a failed tag check
Source: CVE Program / CVE List V5
Vulnerability Description
Release of unverified plaintext in the CCM (CcmBlockCipher) and DSTU 7624 CCM (KCcmBlockCipher) AEAD modes in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker to obtain decryptions of ciphertexts of their choosing via forged messages sent to an application that lets the output buffer of a failed decryption be observed, for example through buffer reuse or logging, because decryption wrote the recovered plaintext into the caller-supplied output buffer before checking the authentication tag and left it there when the check failed. Only decryption into a caller-supplied buffer is affected; methods that return a newly allocated array are not.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
完整性检查值验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Legion of the Bouncy Castle Inc. bc-csharp 0 ~ 2.7.0 -

II. Public POCs for CVE-2026-103601

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III. Intelligence Information for CVE-2026-103601

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Patches & Fixes for CVE-2026-103601 (2)

Vendor Advisories for CVE-2026-103601 (1)

Same Patch Batch · Legion of the Bouncy Castle Inc. · 2026-10-02 · 24 CVEs total

CVE-2026-63569 9.1 CRITICAL MTI/A0 DHAgreement does not validate the peer's ephemeral value
CVE-2026-16000 8.7 HIGH KCcmBlockCipher (DSTU 7624 CCM) tag not bound to nonce when no associated data is used
CVE-2026-63571 8.7 HIGH Attribute certificate path validation does not verify the attribute certificate's signatur
CVE-2026-63566 8.7 HIGH DTLS handshake reassembler allocates buffer from unchecked 24-bit length
CVE-2026-63574 8.7 HIGH Unbounded allocation from OpenPGP signature and user attribute subpacket lengths
CVE-2026-63568 8.7 HIGH Unbounded CMP/CRMF password-based MAC iteration count allows CPU exhaustion
CVE-2026-103600 8.7 HIGH Unbounded ASN.1 nesting depth causes process-terminating stack overflow
CVE-2026-103604 8.7 HIGH Quadratic-time escaping when converting X.509 distinguished names to strings
CVE-2026-103603 8.7 HIGH Unbounded HSS public key level count allows huge array allocation during signature verific
CVE-2026-17507 8.7 HIGH MLS membership checks compare a uint32 leaf_index as signed, admitting an out-of-range sen
CVE-2026-18036 8.2 HIGH NTRU leaks private key information by reducing secret values with a non-constant-time inte
CVE-2026-63577 8.2 HIGH Name Constraints bypass: directoryName constraint matched at any position in the DN instea
CVE-2026-63576 8.2 HIGH URI name constraints checked against a mis-parsed host
CVE-2026-63573 8.2 HIGH Bleichenbacher padding oracle in CMS RSA PKCS#1 v1.5 key-transport unwrap
CVE-2026-103602 8.2 HIGH Name constraints bypass via trailing dot in rfc822Name, dNSName and URI hosts
CVE-2026-63567 8.2 HIGH IesEngine block-cipher mode checks padding before MAC (CBC padding oracle)
CVE-2026-15999 8.2 HIGH AES-CCM decryption accepts zero or out-of-range tag length, bypassing authentication
CVE-2026-16001 8.2 HIGH IesEngine stream-mode MAC forgery via length-dependent KDF split
CVE-2026-63578 7.1 HIGH Unbounded PBE iteration count when decrypting PKCS#8 private keys
CVE-2026-63570 7.1 HIGH Pkcs12Store.GetCertificateChain loops forever on cyclic issuer links

Showing top 20 of 24 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: bc-csharp
Same vendor: Legion of the Bouncy Castle Inc.
Same weakness: CWE-354

V. Comments for CVE-2026-103601

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