Vulnerability · Published Sep 4, 2026 · Assigned by redhat
CVE-2026-85769Libtpms: libtpms: heap out-of-bounds read in tpm2 state unmarshalling via unchecked block_skip_read() blocksize
Medium 6.5
In plain English
A medium-severity out-of-bounds read in Red Hat Enterprise Linux 10 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libtpms | no fix listed | DEBIAN-CVE-2026-85769 |
| Debian:13 | libtpms | no fix listed | DEBIAN-CVE-2026-85769 |
| Debian:14 | libtpms | no fix listed | DEBIAN-CVE-2026-85769 |
| Ubuntu:22.04:LTS | libtpms | no fix listed | UBUNTU-CVE-2026-85769 |
| Ubuntu:24.04:LTS | libtpms | no fix listed | UBUNTU-CVE-2026-85769 |
| Ubuntu:26.04:LTS | libtpms | no fix listed | UBUNTU-CVE-2026-85769 |
| Ubuntu:26.10 | libtpms | no fix listed | UBUNTU-CVE-2026-85769 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Red Hat | Red Hat Enterprise Linux 10 | see references |
| Red Hat | Red Hat Enterprise Linux 8 | see references |
| Red Hat | Red Hat Enterprise Linux 9 | see references |
Weakness: CWE-125 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://access.redhat.com/security/cve/CVE-2026-85769 vdb-entry, x_refsource_REDHAT
- RHBZ#2528538 issue-tracking, x_refsource_REDHAT
- https://github.com/stefanberger/libtpms/commit/b1462888180d896af03cae0487e8d45009cc445e
- https://github.com/stefanberger/libtpms/issues/614
- https://github.com/stefanberger/libtpms/pull/613