Dear Qubes Community,
We have published [Qubes Security Bulletin (QSB) 107: Multiple CPU branch prediction vulnerabilities](qubes-secpack/QSBs/qsb-107-2025.txt at 750ad7196b72dd30c1377a95af2fed3bb4844028 · QubesOS/qubes-secpack · GitHub). The text of this QSB and its accompanying cryptographic signatures are reproduced below, followed by a general explanation of this announcement and authentication instructions.
## Qubes Security Bulletin 107
---===[ Qubes Security Bulletin 107 ]===---
2025-05-15
Multiple CPU branch prediction vulnerabilities
User action
------------
Continue to update normally [1] in order to receive the security updates
described in the "Patching" section below. No other user action is
required in response to this QSB.
Summary
--------
Multiple organizations have recently reported vulnerabilities that
affect CPU branch prediction behavior. Common among these
vulnerabilities is their ability to allow an attacker to manipulate the
branch prediction of the CPU to mount a speculative execution attack
(like the original Spectre v2 attack) even with existing mitigations
enabled.
On 2025-05-12, researchers from the Systems and Network Security Group
at Vrije Universiteit Amsterdam (VUSec) published "Training Solo," [3]
which includes the following:
- Indirect Target Selection (ITS; CVE-2024-28956, XSA-469 [5], part of
INTEL-SA-01153 [7])
- Lion Cove BPU issue (CVE-2025-24495, part of INTEL-SA-01322 [8])
- IP-based attacks
- History-based attacks
On 2025-05-13, researchers from the computer security group at ETH
Zürich (COMSEC) published "Branch Privilege Injection: Exploiting Branch
Predictor Race Conditions" [4] (BPRC; CVE-2024-45332, XSN-3 [6], part of
INTEL-SA-01247 [9])
In addition to the coordinated disclosures above, Intel also reported
internally discovering the following:
- CVE-2025-20623 (part of INTEL-SA-01247 [9])
- CVE-2024-43420 (part of INTEL-SA-01247 [9])
See the linked publications for further details.
Impact
-------
History-based attacks are believed not to affect Xen. [5]
For all other vulnerabilities mentioned, on affected systems, an
attacker who manages to compromise a qube may be able to use it to infer
the contents of arbitrary system memory, including memory assigned to
other qubes.
Affected systems
-----------------
Only systems with Intel CPUs are believed to be affected. According to
Intel's descriptions:
- ITS affects Intel CPUs from Whiskey Lake (8th Generation Intel Core)
to Tiger Lake (11th Generation Intel Core). [7]
- The Lion Cove BPU issue affects Intel Lunar Lake and Arrow Lake (Core
Ultra Series 2) models. [8]
- BPRC affects most Intel CPUs since 8th Generation Intel Core (but see
the caveat below). [9]
- CVE-2025-20623 affects some 10th Generation Intel Core CPUs. [9]
- CVE-2024-43420 affects some Intel Atom CPUs. [9]
See the linked Intel security advisories for more complete and detailed
lists of affected CPU models.
Note: The information above is based on Intel's security advisories. In
general, Intel assesses whether a vulnerability affects a given CPU
model only if that model still receives microcode updates. Therefore, if
a given CPU model no longer receives microcode updates, one should not
infer that a vulnerability does not affect that model merely because
Intel does not report it as affected. In particular, COMSEC observed
that BPRC affects CPUs as far back as 7th Generation Intel Core. [4]
To determine whether your CPU still receives microcode updates, see
"Changes in Customer Support and Servicing Updates for Select Intel
Processors," [10] or check your model's official Intel product page for
an "End of Servicing Updates" (ESU) date. Note that only models that
have reached or will soon reach their ESU date have an ESU date listed.
Newer models that are still fully supported typically have no ESU date
listed.
Patching
---------
The following packages contain security updates that, when applied to
systems with Intel CPUs that still receive microcode updates, will
address the vulnerabilities described in this bulletin:
For Qubes 4.2, in dom0:
- Xen packages, version 4.17.5-7
- microcode_ctl version 2.1.20250512
These packages will migrate from the security-testing repository to the
current (stable) repository over the next two weeks after being tested
by the community. [2] Once available, the packages should be installed
via the Qubes Update tool or its command-line equivalents. [1]
Dom0 must be restarted afterward in order for the updates to take
effect.
If you use Anti Evil Maid, you will need to reseal your secret
passphrase to new PCR values, as PCR18+19 will change due to the new Xen
binaries.
Credits
--------
See the original Xen Security Advisory.
References
-----------
[1] https://www.qubes-os.org/doc/how-to-update/
[2] https://www.qubes-os.org/doc/testing/
[3] https://vusec.net/projects/training-solo
[4] https://comsec.ethz.ch/research/microarch/branch-privilege-injection/
[5] https://xenbits.xen.org/xsa/advisory-469.html
[6] https://lists.xenproject.org/archives/html/xen-devel/2025-05/msg00632.html
[7] https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-01153.html
[8] https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-01322.html
[9] https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-01247.html
[10] https://www.intel.com/content/www/us/en/support/articles/000022396/processors.html
--
The Qubes Security Team
https://www.qubes-os.org/security/
*Source*: [qsb-107-2025.txt](qubes-secpack/QSBs/qsb-107-2025.txt at 750ad7196b72dd30c1377a95af2fed3bb4844028 · QubesOS/qubes-secpack · GitHub)
## [Marek Marczykowski-Górecki](Team | Qubes OS)'s PGP signature
*Source*: [qsb-107-2025.txt.sig.simon](qubes-secpack/QSBs/qsb-107-2025.txt.sig.simon at 750ad7196b72dd30c1377a95af2fed3bb4844028 · QubesOS/qubes-secpack · GitHub)
## What is the purpose of this announcement?
The purpose of this announcement is to inform the Qubes community that a new Qubes security bulletin (QSB) has been published.
## What is a Qubes security bulletin (QSB)?
A Qubes security bulletin (QSB) is a security announcement issued by the [Qubes security team](Qubes OS project security center | Qubes OS). A QSB typically provides a summary and impact analysis of one or more recently-discovered software vulnerabilities, including details about patching to address them. For a list of all QSBs, see [Qubes security bulletins (QSBs)](Qubes security bulletins (QSBs) | Qubes OS).
## Why should I care about QSBs?
QSBs tell you what actions you must take in order to protect yourself from recently-discovered security vulnerabilities. In most cases, security vulnerabilities are addressed by [updating normally](How to update | Qubes OS). However, in some cases, special user action is required. In all cases, the required actions are detailed in QSBs.
## What are the PGP signatures that accompany QSBs?
A [PGP](Pretty Good Privacy - Wikipedia) signature is a cryptographic [digital signature](Digital signature - Wikipedia) made in accordance with the [OpenPGP](Pretty Good Privacy - Wikipedia) standard. PGP signatures can be cryptographically verified with programs like [GNU Privacy Guard (GPG)](https://gnupg.org/). The Qubes security team cryptographically signs all QSBs so that Qubes users have a reliable way to check whether QSBs are genuine. The only way to be certain that a QSB is authentic is by verifying its PGP signatures.
## Why should I care whether a QSB is authentic?
A forged QSB could deceive you into taking actions that adversely affect the security of your Qubes OS system, such as installing malware or making configuration changes that render your system vulnerable to attack. Falsified QSBs could sow fear, uncertainty, and doubt about the security of Qubes OS or the status of the Qubes OS Project.
## How do I verify the PGP signatures on a QSB?
The following command-line instructions assume a Linux system with `git` and `gpg` installed. (For Windows and Mac options, see [OpenPGP software](Verifying signatures | Qubes OS).)
1. Obtain the Qubes Master Signing Key (QMSK), e.g.:
$ gpg --fetch-keys https://keys.qubes-os.org/keys/qubes-master-signing-key.asc
gpg: directory '/home/user/.gnupg' created
gpg: keybox '/home/user/.gnupg/pubring.kbx' created
gpg: requesting key from 'https://keys.qubes-os.org/keys/qubes-master-signing-key.asc'
gpg: /home/user/.gnupg/trustdb.gpg: trustdb created
gpg: key DDFA1A3E36879494: public key "Qubes Master Signing Key" imported
gpg: Total number processed: 1
gpg: imported: 1
(For more ways to obtain the QMSK, see [How to import and authenticate the Qubes Master Signing Key](Verifying signatures | Qubes OS).)
2. View the fingerprint of the PGP key you just imported. (Note: `gpg>` indicates a prompt inside of the GnuPG program. Type what appears after it when prompted.)
$ gpg --edit-key 0x427F11FD0FAA4B080123F01CDDFA1A3E36879494
gpg (GnuPG) 2.2.27; Copyright (C) 2021 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
pub rsa4096/DDFA1A3E36879494
created: 2010-04-01 expires: never usage: SC
trust: unknown validity: unknown
[ unknown] (1). Qubes Master Signing Key
> fpr
pub rsa4096/DDFA1A3E36879494 2010-04-01 Qubes Master Signing Key
Primary key fingerprint: 427F 11FD 0FAA 4B08 0123 F01C DDFA 1A3E 3687 9494
3. *Important*: At this point, you still don't know whether the key you just imported is the genuine QMSK or a forgery. In order for this entire procedure to provide meaningful security benefits, you *must* authenticate the QMSK out-of-band. *Do not skip this step*! The standard method is to obtain the QMSK fingerprint from *multiple independent sources in several different ways* and check to see whether they match the key you just imported. For more information, see [How to import and authenticate the Qubes Master Signing Key](Verifying signatures | Qubes OS).
*Tip*: After you have authenticated the QMSK out-of-band to your satisfaction, record the QMSK fingerprint in a safe place (or several) so that you don't have to repeat this step in the future.
4. Once you are satisfied that you have the genuine QMSK, set its trust level to 5 ("ultimate"), then quit GnuPG with `q`.
> trust
pub rsa4096/DDFA1A3E36879494
created: 2010-04-01 expires: never usage: SC
trust: unknown validity: unknown
[ unknown] (1). Qubes Master Signing Key
Please decide how far you trust this user to correctly verify other users' keys
(by looking at passports, checking fingerprints from different sources, etc.)
1 = I don't know or won't say
2 = I do NOT trust
3 = I trust marginally
4 = I trust fully
5 = I trust ultimately
m = back to the main menu
Your decision? 5
Do you really want to set this key to ultimate trust? (y/N) y
pub rsa4096/DDFA1A3E36879494
created: 2010-04-01 expires: never usage: SC
trust: ultimate validity: unknown
[ unknown] (1). Qubes Master Signing Key
Please note that the shown key validity is not necessarily correct
unless you restart the program.
> q
5. Use Git to clone the qubes-secpack repo.
$ git clone https://github.com/QubesOS/qubes-secpack.git
Cloning into 'qubes-secpack'...
remote: Enumerating objects: 4065, done.
remote: Counting objects: 100% (1474/1474), done.
remote: Compressing objects: 100% (742/742), done.
remote: Total 4065 (delta 743), reused 1413 (delta 731), pack-reused 2591
Receiving objects: 100% (4065/4065), 1.64 MiB | 2.53 MiB/s, done.
Resolving deltas: 100% (1910/1910), done.
6. Import the included PGP keys. (See our [PGP key policies](Qubes security pack (qubes-secpack) | Qubes OS) for important information about these keys.)
$ gpg --import qubes-secpack/keys/*/*
gpg: key 063938BA42CFA724: public key "Marek Marczykowski-Górecki (Qubes OS signing key)" imported
gpg: qubes-secpack/keys/core-devs/retired: read error: Is a directory
gpg: no valid OpenPGP data found.
gpg: key 8C05216CE09C093C: 1 signature not checked due to a missing key
gpg: key 8C05216CE09C093C: public key "HW42 (Qubes Signing Key)" imported
gpg: key DA0434BC706E1FCF: public key "Simon Gaiser (Qubes OS signing key)" imported
gpg: key 8CE137352A019A17: 2 signatures not checked due to missing keys
gpg: key 8CE137352A019A17: public key "Andrew David Wong (Qubes Documentation Signing Key)" imported
gpg: key AAA743B42FBC07A9: public key "Brennan Novak (Qubes Website & Documentation Signing)" imported
gpg: key B6A0BB95CA74A5C3: public key "Joanna Rutkowska (Qubes Documentation Signing Key)" imported
gpg: key F32894BE9684938A: public key "Marek Marczykowski-Górecki (Qubes Documentation Signing Key)" imported
gpg: key 6E7A27B909DAFB92: public key "Hakisho Nukama (Qubes Documentation Signing Key)" imported
gpg: key 485C7504F27D0A72: 1 signature not checked due to a missing key
gpg: key 485C7504F27D0A72: public key "Sven Semmler (Qubes Documentation Signing Key)" imported
gpg: key BB52274595B71262: public key "unman (Qubes Documentation Signing Key)" imported
gpg: key DC2F3678D272F2A8: 1 signature not checked due to a missing key
gpg: key DC2F3678D272F2A8: public key "Wojtek Porczyk (Qubes OS documentation signing key)" imported
gpg: key FD64F4F9E9720C4D: 1 signature not checked due to a missing key
gpg: key FD64F4F9E9720C4D: public key "Zrubi (Qubes Documentation Signing Key)" imported
gpg: key DDFA1A3E36879494: "Qubes Master Signing Key" not changed
gpg: key 1848792F9E2795E9: public key "Qubes OS Release 4 Signing Key" imported
gpg: qubes-secpack/keys/release-keys/retired: read error: Is a directory
gpg: no valid OpenPGP data found.
gpg: key D655A4F21830E06A: public key "Marek Marczykowski-Górecki (Qubes security pack)" imported
gpg: key ACC2602F3F48CB21: public key "Qubes OS Security Team" imported
gpg: qubes-secpack/keys/security-team/retired: read error: Is a directory
gpg: no valid OpenPGP data found.
gpg: key 4AC18DE1112E1490: public key "Simon Gaiser (Qubes Security Pack signing key)" imported
gpg: Total number processed: 17
gpg: imported: 16
gpg: unchanged: 1
gpg: marginals needed: 3 completes needed: 1 trust model: pgp
gpg: depth: 0 valid: 1 signed: 6 trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: depth: 1 valid: 6 signed: 0 trust: 6-, 0q, 0n, 0m, 0f, 0u
7. Verify signed Git tags.
$ cd qubes-secpack/
$ git tag -v `git describe`
object 266e14a6fae57c9a91362c9ac784d3a891f4d351
type commit
tag marmarek_sec_266e14a6
tagger Marek Marczykowski-Górecki 1677757924 +0100
Tag for commit 266e14a6fae57c9a91362c9ac784d3a891f4d351
gpg: Signature made Thu 02 Mar 2023 03:52:04 AM PST
gpg: using RSA key 2D1771FE4D767EDC76B089FAD655A4F21830E06A
gpg: Good signature from "Marek Marczykowski-Górecki (Qubes security pack)" [full]
The exact output will differ, but the final line should always start with `gpg: Good signature from...` followed by an appropriate key. The `[full]` indicates full trust, which this key inherits in virtue of being validly signed by the QMSK.
8. Verify PGP signatures, e.g.:
$ cd QSBs/
$ gpg --verify qsb-087-2022.txt.sig.marmarek qsb-087-2022.txt
gpg: Signature made Wed 23 Nov 2022 04:05:51 AM PST
gpg: using RSA key 2D1771FE4D767EDC76B089FAD655A4F21830E06A
gpg: Good signature from "Marek Marczykowski-Górecki (Qubes security pack)" [full]
$ gpg --verify qsb-087-2022.txt.sig.simon qsb-087-2022.txt
gpg: Signature made Wed 23 Nov 2022 03:50:42 AM PST
gpg: using RSA key EA18E7F040C41DDAEFE9AA0F4AC18DE1112E1490
gpg: Good signature from "Simon Gaiser (Qubes Security Pack signing key)" [full]
$ cd ../canaries/
$ gpg --verify canary-034-2023.txt.sig.marmarek canary-034-2023.txt
gpg: Signature made Thu 02 Mar 2023 03:51:48 AM PST
gpg: using RSA key 2D1771FE4D767EDC76B089FAD655A4F21830E06A
gpg: Good signature from "Marek Marczykowski-Górecki (Qubes security pack)" [full]
$ gpg --verify canary-034-2023.txt.sig.simon canary-034-2023.txt
gpg: Signature made Thu 02 Mar 2023 01:47:52 AM PST
gpg: using RSA key EA18E7F040C41DDAEFE9AA0F4AC18DE1112E1490
gpg: Good signature from "Simon Gaiser (Qubes Security Pack signing key)" [full]
Again, the exact output will differ, but the final line of output from each `gpg --verify` command should always start with `gpg: Good signature from...` followed by an appropriate key.
For this announcement (QSB-107), the commands are:
$ gpg --verify qsb-107-2025.txt.sig.marmarek qsb-107-2025.txt
$ gpg --verify qsb-107-2025.txt.sig.simon qsb-107-2025.txt
You can also verify the signatures directly from this announcement in addition to or instead of verifying the files from the qubes-secpack. Simply copy and paste the QSB-107 text into a plain text file and do the same for both signature files. Then, perform the same authentication steps as listed above, substituting the filenames above with the names of the files you just created.
This announcement is also available on the Qubes website: