crypto: krb5 - filter out async aead implementations at alloc (CVE-2026-64439) | HOL Guard CVE

Critical · CVSS 9.8CVE-2026-64439

crypto: krb5 - filter out async aead implementations at alloc

Answer in brief

CVE-2026-64439 records a Critical severity (CVSS 9.8) vulnerability in crypto: krb5 - filter out async aead implementations at alloc. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 25, 2026Updated Sep 3, 2026Source checked Sep 20, 2026First seen by HOL Aug 5, 2026Material review Sep 3, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:o:linux:linux_kernel::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=00244da40f7821b242c4612428d4192230dba27f <ef6feb77e2d91761427c5b773edc9c97e1b706ad \|\| >=00244da40f7821b242c4612428d4192230dba27f <2b7bd6dccff14b8b632c5244f1fd506918077221 \|\| >=00244da40f7821b242c4612428d4192230dba27f <6c9dddeb582fde005360f4fe02c760d45ca05fb5	ef6feb77e2d91761427c5b773edc9c97e1b706ad, 2b7bd6dccff14b8b632c5244f1fd506918077221, 6c9dddeb582fde005360f4fe02c760d45ca05fb5
Linux/Linuxgeneric	6.15	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to ef6feb77e2d91761427c5b773edc9c97e1b706ad if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 3, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: crypto: krb5 - filter out async aead implementations at alloc krb5_aead_encrypt(), krb5_aead_decrypt() in rfc3961_simplified.c and rfc8009_encrypt(), rfc8009_decrypt() in rfc8009_aes2.c set a NULL completion callback and treat any negative return from crypto_aead_{encrypt,decrypt}() as terminal, falling through to kfree_sensitive(buffer). When the encrypt_name resolves to an async AEAD instance the request returns -EINPROGRESS, the buffer is freed while the backend's worker still holds a pointer, and the worker dereferences the freed slab on completion. KASAN report under UML+SLUB with a synthetic async aead backend bound to krb5->encrypt_name: BUG: KASAN: slab-use-after-free in t5_stub_complete+0x7d/0xc7 The helpers were written synchronously, so filter the async instances out at allocation time instead of plumbing crypto_wait_req() through every call site. Reachable via net/rxrpc/rxgk.c, fs/afs/cm_security.c and net/ceph/crypto.c on systems with an async AEAD provider bound to the krb5 enctype name.

Quoted source text, attributed separately from HOL analysis.