VulnTideExploited vulnerabilities, by vendor. Data as of .
Not in CISA KEVPublished CVSS 8.2 highEPSS 0.3% probability of exploitation in 30 daysFound by AI: Anthropic (Claude)
Legion of the Bouncy Castle

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

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?
0.3%

EPSS score, percentile 22.1 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?
8.2 High

CVSS v4.0 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (3)

Which versions are affected?

Affected

  • before 2.7.0

Versions by product

Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.

What to do

Advisories and patches

This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Legion of the Bouncy Castle Inc. bc-csharp
StatusVersions
Affectedbefore 2.7.0

Versions not listed are: unaffected.

Source: CVE List, as of . About the data.

About this vulnerability

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, b…

Summary: CVE record, as of .

  • CISA has not added CVE-2026-103601 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
  • The CVE record was published on 2 Oct 2026.
  • The CVE record carries a CVSS v4.0 base score of 8.2 (High), given by its CNA.
  • FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.3% (percentile 22.1), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
  • CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
  • The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.

Description

CcmBlockCipher and KCcmBlockCipher leave unverified plaintext in the output buffer after a failed tag check

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 List, as of . About the data.

Weakness

CWE-354
  • CWE-354: Improper Validation of Integrity Check Value

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.

Timeline

DateEvent
CVE record published