CyberSecBulletin
CVE-2022-48980NVD status: Analyzed

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2022-48980 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 7.8 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 5e88c6f4aaa70c542e59e5a9d2244bcc99cd245d, 147f3e3d84054117ae6b9bf317ec4fda9f991192, f8bac7f9fdb0017b32157957ffffd490f95faa07 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.24% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 5e88c6f4aaa70c542e59e5a9d2244bcc99cd245d or 147f3e3d84054117ae6b9bf317ec4fda9f991192 or f8bac7f9fdb0017b32157957ffffd490f95faa07, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.83 or 6.0.13, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux38fbe91f2287c696f290d9115901aa435f7166a8 up to, but not including, 5e88c6f4aaa70c542e59e5a9d2244bcc99cd245d; 38fbe91f2287c696f290d9115901aa435f7166a8 up to, but not including, 147f3e3d84054117ae6b9bf317ec4fda9f991192; 38fbe91f2287c696f290d9115901aa435f7166a8 up to, but not including, f8bac7f9fdb0017b32157957ffffd490f95faa07; 5.145e88c6f4aaa70c542e59e5a9d2244bcc99cd245d, 147f3e3d84054117ae6b9bf317ec4fda9f991192, f8bac7f9fdb0017b32157957ffffd490f95faa07
LinuxLinux Kernel5.14 up to, but not including, 5.15.83; 5.16 up to, but not including, 6.0.13; 6.15.15.83, 6.0.13

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
LowNo special conditions are needed; the attack works reliably.
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:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: net: dsa: sja1105: avoid out of bounds access in sja1105_init_l2_policing() The SJA1105 family has 45 L2 policing table entries (SJA1105_MAX_L2_POLICING_COUNT) and SJA1110 has 110 (SJA1110_MAX_L2_POLICING_COUNT). Keeping the table structure but accounting for the difference in port count (5 in SJA1105 vs 10 in SJA1110) does not fully explain the difference. Rather, the SJA1110 also has L2 ingress policers for multicast traffic. If a packet is classified as multicast, it will be processed by the policer index 99 + SRCPORT. The sja1105_init_l2_policing() function initializes all L2 policers such that they don't interfere with normal packet reception by default. To have a common code between SJA1105 and SJA1110, the index of the multicast policer for the port is calculated because it's an index that is out of bounds for SJA1105 but in bounds for SJA1110, and a bounds check is performed. The code fails to do the proper thing when determining what to do with the multicast policer of port 0 on SJA1105 (ds->num_ports = 5). The "mcast" index will be equal to 45, which is also equal to table->ops->max_entry_count (SJA1105_MAX_L2_POLICING_COUNT). So it passes through the check. But at the same time, SJA1105 doesn't have multicast policers. So the code programs the SHARINDX field of an out-of-bounds element in the L2 Policing table of the static config. The comparison between index 45 and 45 entries should have determined the code to not access this policer index on SJA1105, since its memory wasn't even allocated. With enough bad luck, the out-of-bounds write could even overwrite other valid kernel data, but in this case, the issue was detected using KASAN. Kernel log: sja1105 spi5.0: Probed switch chip: SJA1105Q ================================================================== BUG: KASAN: slab-out-of-bounds in sja1105_setup+0x1cbc/0x2340 Write of size 8 at addr ffffff880bd57708 by task kworker/u8:0/8 ... Workqueue: events_unbound deferred_probe_work_func Call trace: ... sja1105_setup+0x1cbc/0x2340 dsa_register_switch+0x1284/0x18d0 sja1105_probe+0x748/0x840 ... Allocated by task 8: ... sja1105_setup+0x1bcc/0x2340 dsa_register_switch+0x1284/0x18d0 sja1105_probe+0x748/0x840 ...

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.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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