Skip to main content
VulnerabilityPublished Updated

CVE-2026-15999: Improper Validation of Integrity Check Value

Source GCVE Database

0
Authoritative record:CVE-2026-15999· High 8.2

Not known to be exploited · CVSS 8.2 High : upgrade to 2.7.0 soon.

Data as of 27 Oct 2026, 20:26 UTC

CVSS 4.0 base score
8.2High
How severe the flaw is on the 0–10 CVSS scale.
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:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
Legion of the Bouncy Castle Inc.bc-csharpAffected
  • <2.7.0
Fixed in
  • 2.7.0
NuGetBouncyCastle.Cryptographypkg:nuget/BouncyCastle.CryptographyOther threatsAffected
  • <2.7.0
Fixed in
  • 2.7.0

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

Community reviews

Loading reviews…