Junos OS: Out-of-bounds Write
CVE-2024-39556 is a high-severity out-of-bounds write vulnerability in Junos OS from Juniper Networks, with a CVSS 3.1 base score of 7.0 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 21.4R3-S7, 22.1R3-S6, 22.2R3-S4 as the first without the flaw, so updating Junos OS to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.09% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Junos OS to 21.4R3-S7 or 22.1R3-S6 or 22.2R3-S4 or 22.3R3-S3, whichever matches your release line, or a later version.
- Update Junos OS Evolved to 21.4R3-S7-EVO or 22.1R3-S6-EVO or 22.2R3-S4-EVO or 22.3R3-S3-EVO, whichever matches your release line, or a later version.
- Update Junos to 21.4 or a later version.
- Read the advisory on supportportal.juniper.net for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Juniper Networks | Junos OS | before 21.4R3-S7; 22.1 up to, but not including, 22.1R3-S6; 22.2 up to, but not including, 22.2R3-S4; 22.3 up to, but not including, 22.3R3-S3; 22.4 up to, but not including, 22.4R3-S2; 23.2 up to, but not including, 23.2R2; 23.4 up to, but not including, 23.4R1-S1, 23.4R2; before 21.4r3-s7; and 9 more ranges | 21.4R3-S7, 22.1R3-S6, 22.2R3-S4, 22.3R3-S3, 22.4R3-S2, 23.2R2 |
| Juniper Networks | Junos OS Evolved | before 21.4R3-S7-EVO; 22.1-EVO up to, but not including, 22.1R3-S6-EVO; 22.2-EVO up to, but not including, 22.2R3-S4-EVO; 22.3-EVO up to, but not including, 22.3R3-S3-EVO; 22.4-EVO up to, but not including, 22.4R3-S2-EVO; 23.2-EVO up to, but not including, 23.2R2-EVO; 23.4-EVO up to, but not including, 23.4R1-S1-EVO, 23.4R2-EVO; before 21.4r3-s7-evo; and 5 more ranges | 21.4R3-S7-EVO, 22.1R3-S6-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO, 22.4R3-S2-EVO, 23.2R2-EVO |
| Juniper Networks | Junos | before 21.4; 21.4; 22.1; 22.2; 22.3; 22.4; 23.2; 23.4 | 21.4 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 7.1 | High | CNA (juniper.net) |
| CVSS 3.1 | 6.4 | Medium | CNA (juniper.net) |
| CVSS 3.1 | 7.0 | High | NVD |
Official description
A Stack-Based Buffer Overflow vulnerability in Juniper Networks Junos OS and Juniper Networks Junos OS Evolved may allow a local, low-privileged attacker with access to the CLI the ability to load a malicious certificate file, leading to a limited Denial of Service (DoS) or privileged code execution. By exploiting the 'set security certificates' command with a crafted certificate file, a malicious attacker with access to the CLI could cause a crash of the command management daemon (mgd), limited to the local user's command interpreter, or potentially trigger a stack-based buffer overflow. This issue affects: Junos OS: * All versions before 21.4R3-S7, * from 22.1 before 22.1R3-S6, * from 22.2 before 22.2R3-S4, * from 22.3 before 22.3R3-S3, * from 22.4 before 22.4R3-S2, * from 23.2 before 23.2R2, * from 23.4 before 23.4R1-S1, 23.4R2; Junos OS Evolved: * All versions before 21.4R3-S7-EVO, * from 22.1-EVO before 22.1R3-S6-EVO, * from 22.2-EVO before 22.2R3-S4-EVO, * from 22.3-EVO before 22.3R3-S3-EVO, * from 22.4-EVO before 22.4R3-S2-EVO, * from 23.2-EVO before 23.2R2-EVO, * from 23.4-EVO before 23.4R1-S1-EVO, 23.4R2-EVO.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- supportportal.juniper.net/JSA83016Mitigation
Other vulnerabilities in Junos OS
- 7.5 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 8.8 High severity
- 8.8 High severity
- 7.5 High severity
Recent Out-of-bounds Write vulnerabilities
- 7.5 High severity
- 8.2 High severity
- 8.2 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
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