CVE-2017-2522

Score / Severity

9.8

Critical

CVE Descriptions

An issue was discovered in certain Apple products. iOS before 10.3.2 is affected. macOS before 10.12.5 is affected. tvOS before 10.2.1 is affected. watchOS before 3.2.2 is affected. The issue involves the "CoreFoundation" component. It allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via crafted data.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-119	Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.0	9.8	CRITICAL	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H 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 A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from routers). Attack Complexity This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. Low Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component. 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 to carry out an attack. User Interaction This metric captures the requirement for a 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 An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges. Scope Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports. Unchanged An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same. Base: Impact Metrics The Impact metrics refer to the properties of the impacted component. 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. High There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. 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. High There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). 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 that one has in the description of a vulnerability. Environmental Metrics	nvd@nist.gov
V2	7.5		AV:N/AC:L/Au:N/C:P/I:P/A:P	nvd@nist.gov

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

Date	EPSS V0	EPSS V1	EPSS V2 (> 2022-02-04)	EPSS V3 (> 2025-03-07)	EPSS V4 (> 2025-03-17)
2021-04-18	2.14%	–	–	–	–
2021-09-05	–	2.14%	–	–	–
2021-10-17	–	2.14%	–	–	–
2022-01-09	–	2.14%	–	–	–
2022-02-06	–	–	10.06%	–	–
2022-04-03	–	–	10.06%	–	–
2023-02-26	–	–	10.06%	–	–
2023-03-12	–	–	–	3.52%	–
2023-04-02	–	–	–	5.81%	–
2023-05-07	–	–	–	7.81%	–
2023-06-11	–	–	–	7.65%	–
2023-07-23	–	–	–	7.39%	–
2024-02-11	–	–	–	7.39%	–
2024-06-02	–	–	–	7.39%	–
2024-07-14	–	–	–	8.76%	–
2024-12-22	–	–	–	13.71%	–
2025-01-19	–	–	–	13.71%	–
2025-03-18	–	–	–	–	13.05%
2025-03-30	–	–	–	–	13.05%
2025-03-30	–	–	–	–	13.05,%

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org

Date	Percentile
2021-04-18	–
2021-09-05	77%
2021-10-17	78%
2022-01-09	5%
2022-02-06	88%
2022-04-03	94%
2023-02-26	95%
2023-03-12	9%
2023-04-02	92%
2023-05-07	93%
2023-06-11	93%
2023-07-23	93%
2024-02-11	94%
2024-06-02	94%
2024-07-14	95%
2024-12-22	96%
2025-01-19	96%
2025-03-18	94%
2025-03-30	93%
2025-03-30	93%

Exploit information

Exploit Database EDB-ID : 42049

Publication date : 2017-05-22 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1168 The dump today has this list of iOS stuff: https://wikileaks.org/ciav7p1/cms/page_13205587.html Reading through this sounded interesting: """ Buffer Overflow caused by deserialization parsing error in Foundation library Sending a crafted NSArchiver object to any process that calls NSArchive unarchive method will result in a buffer overflow, allowing for ROP. """ So I've spent all day going through initWithCoder: implementations looking for heap corruption :) The unarchiving of NSCharacterSet will call NSCharacterSetCFCharacterSetCreateWithBitmapRepresentation If we pass a large bitmap we can get to the following call multiple times: while (length > 1) { annexSet = (CFMutableCharacterSetRef)__CFCSetGetAnnexPlaneCharacterSet(cset, *(bytes++)); Here's that function (from the quite old CF code, but the disassm still matches) CF_INLINE CFCharacterSetRef __CFCSetGetAnnexPlaneCharacterSet(CFCharacterSetRef cset, int plane) { __CFCSetAllocateAnnexForPlane(cset, plane); if (!__CFCSetAnnexBitmapGetPlane(cset->_annex->_validEntriesBitmap, plane)) { cset->_annex->_nonBMPPlanes[plane - 1] = (CFCharacterSetRef)CFCharacterSetCreateMutable(CFGetAllocator(cset)); __CFCSetAnnexBitmapSetPlane(cset->_annex->_validEntriesBitmap, plane); } return cset->_annex->_nonBMPPlanes[plane - 1]; } note the interesting [plane - 1], however if we just call this with plane = 0 first __CFCSetAllocateAnnexForPlane will set the _nonBMPPlanes to NULL rather than allocating it but if we supply a large enough bitmap such that we can call __CFCSetGetAnnexPlaneCharacterSet twice, passing 1 the first time and 0 the second time then we can reach: cset->_annex->_nonBMPPlanes[plane - 1] = (CFCharacterSetRef)CFCharacterSetCreateMutable(CFGetAllocator(cset)); with plane = 0 leading to writing a pointer to semi-controlled data one qword below the heap allocation _nonBMPPlanes. This PoC is just a crasher but it looks pretty exploitable. The wikileaks dump implies that this kind of bug can be exploited both via IPC and as a persistence mechanism where apps serialize objects to disk. If I come up with a better PoC for one of those avenues I'll attach it later. (note that the actual PoC object is in the other file (longer_patched.bin) tested on MacOS 10.12.3 (16D32) ################################################################################ A few notes on the relevance of these bugs: NSXPC uses the "secure" version of NSKeyedArchiver where the expected types have to be declared upfront by a message receiver. This restricts the NSXPC attack surface for these issues to either places where overly broad base classes are accepted (like NSObject) or to just those services which accept classes with vulnerable deserializers. There are also other services which use NSKeyedArchives in the "insecure" mode (where the receiver doesn't supply a class whitelist.) Some regular (not NSXPC) xpc services use these. In those cases you could use these bugs to escape sandboxes/escalate privileges. Lots of apps serialize application state to NSKeyedArchives and don't use secure coding providing an avenue for memory-corruption based persistence on iOS. Futhermore there seem to be a bunch of serialized archives on the iPhone which you can touch via the services exposed by lockdownd (over the USB cable) providing an avenue for "local" exploitation (jumping from a user's desktop/laptop to the phone.) The host computer would need to have a valid pairing record to do this without prompts. For example the following files are inside the AFC jail: egrep -Rn NSKeyedArchiver * Binary file Downloads/downloads.28.sqlitedb matches Binary file Downloads/downloads.28.sqlitedb-wal matches Binary file PhotoData/AlbumsMetadata/0F31509F-271A-45BA-9E1F-C6F7BC4A537F.foldermetadata matches Binary file PhotoData/FacesMetadata/NVP_HIDDENFACES.hiddenfacemetadata matches 00006890 | 24 76 65 72 73 69 6F 6E 58 24 6F 62 6A 65 63 74 | $versionX$object 000068A0 | 73 59 24 61 72 63 68 69 76 65 72 54 24 74 6F 70 | sY$archiverT$top Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/42049.zip