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CVE-2026-64375
proc: protect ptrace_may_access() with exec_update_lock (FD links)
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem fs/proc. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64375 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4720-1 · 2026-08-05 · text | 6.1.180-1 | Update the kernel and reboot. DLA-4720-1 shipped the fix on 2026-08-05, in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6405-1 · 2026-07-31 · text | 6.12.100-1 | Update the kernel and reboot. DSA-6405-1 shipped the fix on 2026-07-31, in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
proc_pid_get_link() and proc_pid_readlink() currently look up the task from the pid once, then do the ptrace access check on that task, then look up the task from the pid a second time to do the actual access. That's racy in several ways. To fix it, pass the task to the ->proc_get_link() handler, and instead of proc_fd_access_allowed(), introduce a new helper call_proc_get_link() that looks up and locks the task, does the access check, and calls ->proc_get_link().
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
fs/proc/base.c
fs/proc/fd.c
fs/proc/internal.h
- What this is
- PROC FILESYSTEMMAINTAINERS section matched on fs/proc/ · linux-kernel@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_PROC_FS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_PROC_FS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-25 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.14%, higher than 2.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/proc
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.18 | 5.10.261 | 6253dfee5afb |
| 2.6.18 | 5.15.212 | 65bf0d2b6e91 |
| 2.6.18 | 6.1.178 | de497d7aa2fa |
| 2.6.18 | 6.6.145 | 138c692d2b2d |
| 2.6.18 | 6.12.97 | 83b17872e316 |
| 2.6.18 | 6.18.40 | 497c6bae5167 |
| 2.6.18 | 7.1.4 | dfd1894cb64c |
| 2.6.18 | 7.2 | 6255da28d4bb |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
| DLA-4723-1 | 2026-08-07 | bullseye 6.1.180-1~deb11u1 | tracker |
| DLA-4720-1 | 2026-08-05 | bookworm 6.1.180-1 | tracker |
| DLA-4717-1 | 2026-08-05 | bullseye 5.10.262-1 | tracker |
| DSA-6405-1 | 2026-07-31 | trixie 6.12.100-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- Exploitation uses local open/openat or readlink syscalls against /proc/$pid symlinks; no network or physical access path reaches the flaw.
- AC:LAttack complexity, low
- The attacker can launch the setuid target process and race concurrent procfs accesses repeatedly, thereby controlling both sides of the race.
- PR:LPrivileges required, low
- A basic unprivileged user can pass the initial ptrace check against a same-UID dumpable child before it performs privileged exec; no capability is required.
- UI:NUser interaction, none
- The attacker can create and race the target by launching the setuid program directly, without action from another user.
- S:UScope, unchanged
- The procfs authorization bypass compromises privileged resources on the same host and constitutes ordinary local privilege escalation rather than crossing a VM or hardware isolation boundary.
- C:HConfidentiality impact, high
- The race can redirect an authorized pre-exec lookup to a private post-setuid memfd whose permissive shmem inode allows the attacker to read all privileged contents, including secrets.
- I:HIntegrity impact, high
- The attacker can obtain write and truncation access to the privileged memfd; corruption of trusted data or executable content consumed by the setuid process can yield root-level code execution.
- A:HAvailability impact, high
- Tampering with a privileged process's trusted memfd can crash or disable critical privileged services, and resulting root-level execution permits complete system availability loss.