CVE-2026-99083 ksmbd: fix heap out-of-bounds write in krb5_authenticate()
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99083?
CVE-2026-99083 is a high-severity vulnerability in Linux, published on 23 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix heap out-of-bounds write in krb5_authenticate()
In krb5_authenticate(), out_len is calculated to determine available headroom in response_buf for the incoming Kerberos AP-REP token. However, when SMB2_SESSION_SETUP is processed as a non-first element of a compounded SMB2 request, the calculation omits work->next_smb2_rsp_hdr_off.
This causes out_len to overstate remaining buffer headroom by the cumulative size of prior responses in the compound chain. Consequently, the length check in ksmbd_krb5_authenticate() (*out_len <= resp->spnego_blob_len) passes erroneously, allowing memcpy() to write the AP-REP blob past the end of response_buf into adjacent kernel heap memory.
Fix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len, ensuring it accurately reflects physical remaining buffer space.
Which versions are affected by CVE-2026-99083?
How do I fix CVE-2026-99083?
Upgrade to a fixed version.
Is CVE-2026-99083 being exploited?
There is no known exploitation of CVE-2026-99083 in the wild and no public exploit code.
Sources
Also known as AZL-110990, BELL-CVE-2026-99083, DEBIAN-CVE-2026-99083, GHSA-2j87-48p3-j5xw, UBUNTU-CVE-2026-99083.