CVE-2026-15999: Improper Validation of Integrity Check Value
Source GCVE Database
Not known to be exploited · CVSS 8.2 High : upgrade to 2.7.0 soon.
Data as of 27 Oct 2026, 20:26 UTC
- Patch
- Available – fixed in 2.7.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 2 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade bc-csharp and BouncyCastle.Cryptography to 2.7.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Legion of the Bouncy Castle Inc.bc-csharp | Affected
| Fixed in
|
NuGetBouncyCastle.Cryptographypkg:nuget/BouncyCastle.CryptographyOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, users should avoid using vulnerable versions of bc-csharp for AES-CCM encryption or implement additional integrity validation mechanisms if feasible.
Description
A vulnerability in the AES-CCM implementation of Legion of the Bouncy Castle Inc. bc-csharp before version 2.7.0 allows an attacker to modify encrypted content without detection. This occurs due to improper validation of the integrity check value when the authentication tag length is zero or outside the expected range defined by RFC 5084. The flaw affects decryption processes that accept unchecked tag lengths, enabling undetected tampering of CCM-encrypted data.
References
- nvd.nist.gov/vuln/detail/CVE-2026-15999 (opens in a new tab)
- github.com/bcgit/bc-csharp/commit/2818bdfa55efd58b0d6a1c75f360b8404d879780 (opens in a new tab)
- github.com/bcgit/bc-csharp/commit/9d284d8f379614def853b590c62bbb31c48f7af0 (opens in a new tab)
- github.com/bcgit/bc-csharp/wiki/CVE-2026-15999 (opens in a new tab)