GSS-NTLMSSP is a mechglue plugin for the GSSAPI library that implements NTLM authentication. Prior to version 1.2.0, multiple out-of-bounds reads when decoding NTLM fields can trigger a denial of service. A 32-bit integer overflow condition can lead to incorrect checks of consistency of length of internal buffers. Although most applications will error out before accepting a singe input buffer of 4GB in length this could theoretically happen. This vulnerability can be triggered via the main gss_accept_sec_context entry point if the application allows tokens greater than 4GB in length. This can lead to a large, up to 65KB, out-of-bounds read which could cause a denial-of-service if it reads from unmapped memory. Version 1.2.0 contains a patch for the out-of-bounds reads.
Weakness
The product reads data past the end, or before the beginning, of the intended buffer.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Gss-ntlmssp |
Gss-ntlmssp_project |
* |
1.2.0 (excluding) |
| Red Hat Enterprise Linux 8 |
RedHat |
gssntlmssp-0:1.2.0-1.el8_8 |
* |
| Gss-ntlmssp |
Ubuntu |
bionic |
* |
| Gss-ntlmssp |
Ubuntu |
esm-apps/bionic |
* |
| Gss-ntlmssp |
Ubuntu |
esm-apps/focal |
* |
| Gss-ntlmssp |
Ubuntu |
esm-apps/jammy |
* |
| Gss-ntlmssp |
Ubuntu |
esm-apps/xenial |
* |
| Gss-ntlmssp |
Ubuntu |
focal |
* |
| Gss-ntlmssp |
Ubuntu |
jammy |
* |
| Gss-ntlmssp |
Ubuntu |
kinetic |
* |
| Gss-ntlmssp |
Ubuntu |
lunar |
* |
| Gss-ntlmssp |
Ubuntu |
mantic |
* |
| Gss-ntlmssp |
Ubuntu |
trusty |
* |
| Gss-ntlmssp |
Ubuntu |
upstream |
* |
| Gss-ntlmssp |
Ubuntu |
xenial |
* |
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.
References