CyberSecBulletin
CVE-2024-56558NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2024-56558 is a high-severity use after free 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 e2fa0d0e327279a8defb87b263cd0bf288fd9261, 7fd29d284b55c2274f7a748e6c5f25b4758b8da5, 6cefcadd34e3c71c81ea64b899a0daa86314a51a 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 e2fa0d0e327279a8defb87b263cd0bf288fd9261 or 7fd29d284b55c2274f7a748e6c5f25b4758b8da5 or 6cefcadd34e3c71c81ea64b899a0daa86314a51a or 7d8f7816bebcd2e7400bb4d786eccb8f33c9f9ec, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.4.287 or 5.10.231 or 5.15.174 or 6.1.120, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxbf18f163e89c52e09c96534db45c4274273a0b34 up to, but not including, e2fa0d0e327279a8defb87b263cd0bf288fd9261; bf18f163e89c52e09c96534db45c4274273a0b34 up to, but not including, 7fd29d284b55c2274f7a748e6c5f25b4758b8da5; bf18f163e89c52e09c96534db45c4274273a0b34 up to, but not including, 6cefcadd34e3c71c81ea64b899a0daa86314a51a; bf18f163e89c52e09c96534db45c4274273a0b34 up to, but not including, 7d8f7816bebcd2e7400bb4d786eccb8f33c9f9ec; bf18f163e89c52e09c96534db45c4274273a0b34 up to, but not including, 1cecfdbc6bfc89c516d286884c7f29267b95de2b; bf18f163e89c52e09c96534db45c4274273a0b34 up to, but not including, 7365d1f8de63cffdbbaa2287ce0205438e1a922f; bf18f163e89c52e09c96534db45c4274273a0b34 up to, but not including, be8f982c369c965faffa198b46060f8853e0f1f0; 3.17e2fa0d0e327279a8defb87b263cd0bf288fd9261, 7fd29d284b55c2274f7a748e6c5f25b4758b8da5, 6cefcadd34e3c71c81ea64b899a0daa86314a51a, 7d8f7816bebcd2e7400bb4d786eccb8f33c9f9ec, 1cecfdbc6bfc89c516d286884c7f29267b95de2b, 7365d1f8de63cffdbbaa2287ce0205438e1a922f
LinuxLinux Kernel3.17 up to, but not including, 5.4.287; 5.5 up to, but not including, 5.10.231; 5.11 up to, but not including, 5.15.174; 5.16 up to, but not including, 6.1.120; 6.2 up to, but not including, 6.6.64; 6.7 up to, but not including, 6.12.45.4.287, 5.10.231, 5.15.174, 6.1.120, 6.6.64, 6.12.4

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
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 CISA (ADP).

Official description

In the Linux kernel, the following vulnerability has been resolved: nfsd: make sure exp active before svc_export_show The function `e_show` was called with protection from RCU. This only ensures that `exp` will not be freed. Therefore, the reference count for `exp` can drop to zero, which will trigger a refcount use-after-free warning when `exp_get` is called. To resolve this issue, use `cache_get_rcu` to ensure that `exp` remains active. ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 3 PID: 819 at lib/refcount.c:25 refcount_warn_saturate+0xb1/0x120 CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb1/0x120 ... Call Trace: <TASK> e_show+0x20b/0x230 [nfsd] seq_read_iter+0x589/0x770 seq_read+0x1e5/0x270 vfs_read+0x125/0x530 ksys_read+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

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

References

Recent Use After Free vulnerabilities

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