CVE-2026-85769 Libtpms: libtpms: heap out-of-bounds read in tpm2 state unmarshalling via unchecked block_skip_read() blocksize
Description
A flaw was found in libtpms, a library that provides software TPM 2.0 emulation. When restoring TPM 2.0 state (for example during a virtual machine's power-on or state/migration restore), a malformed state blob can supply an oversized skip-block length that is not validated against the remaining size of the input buffer. This can drive an internal size counter negative, which bypasses a subsequent bounds check due to an unsafe signed-to-unsigned conversion, causing the parser to read memory outside the bounds of the heap buffer holding the state data. Successful exploitation can crash the process hosting libtpms (such as swtpm), resulting in a denial of service of the emulated TPM device and the virtual machine that depends on it. No data corruption or information disclosure was confirmed.
CVSS 3.1 detail
Vector CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitable from the adjacent network, without an account and without any user action; an attacker can seriously compromise confidentiality, integrity or availability.
- Attack vector
- Adjacent network
- Attack complexity
- Low
- Privileges required
- None
- Interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| Red Hat Enterprise Linux 10 | Versions not published | |
| Red Hat Enterprise Linux 8 | Versions not published | |
| Red Hat Enterprise Linux 9 | Versions not published |