CVE-2026-75900

An out-of-bounds read vulnerability was found in swtpm's SWTPM_NVRAM_CheckHeader() function. The entry guard checks the buffer length against sizeof(bh), where bh is a pointer, instead of sizeof(*bh), the actual struct size. This allows an undersized buffer to pass validation, causing a 2-byte heap overread on 64-bit systems (6 bytes on 32-bit) when accessing the totlen field. This may cause daemon termination on some platforms and leaks heap data to the log.

Red Hat rates this issue as Moderate impact. The SWTPM_NVRAM_CheckHeader() function in swtpm uses sizeof(bh) where bh is a pointer, checking buffer length against 8 bytes (on 64-bit) instead of the 10-byte packed blobheader struct. An attacker with access to the control channel can send an 8-byte state blob that passes this guard; the subsequent read of bh->totlen at offset 6 overreads the heap allocation by 2 bytes. The out-of-bounds value is then printed to the swtpm log, leaking a small amount of adjacent heap data. This is distinct from CVE-2022-23645, which added validation on the hdrsize field below this guard but did not fix the entry length check.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Fixed version: 0.10.2