Linux: Use After Free
CVE-2022-49287 is a high-severity use after free vulnerability in Linux, 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 473a66f99cb8173c14138c5a5c69bfad04e8f9ac, cb64bd038beacb4331fe464a36c8b5481e8f51e2, a27ed2f3695baf15f9b34d2d7a1f9fc105539a81 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 0.27% 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 Linux to 473a66f99cb8173c14138c5a5c69bfad04e8f9ac or cb64bd038beacb4331fe464a36c8b5481e8f51e2 or a27ed2f3695baf15f9b34d2d7a1f9fc105539a81 or 290e05f346d1829e849662c97e42d5ad984f5258, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.14.276 or 4.19.238 or 5.4.189 or 5.10.110, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, 473a66f99cb8173c14138c5a5c69bfad04e8f9ac; fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, cb64bd038beacb4331fe464a36c8b5481e8f51e2; fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, a27ed2f3695baf15f9b34d2d7a1f9fc105539a81; fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, 290e05f346d1829e849662c97e42d5ad984f5258; fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, 662893b4f6bd466ff9e1cd454c44c26d32d554fe; fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, 2f928c0d5c02dbab49e8c19d98725c822f6fc409; fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, 6e7baf84149fb43950631415de231b3a41915aa3; fdc915f7f71939ad5a3dda3389b8d2d7a7c5ee66 up to, but not including, 7e0438f83dc769465ee663bb5dcf8cc154940712; and 1 more ranges | 473a66f99cb8173c14138c5a5c69bfad04e8f9ac, cb64bd038beacb4331fe464a36c8b5481e8f51e2, a27ed2f3695baf15f9b34d2d7a1f9fc105539a81, 290e05f346d1829e849662c97e42d5ad984f5258, 662893b4f6bd466ff9e1cd454c44c26d32d554fe, 2f928c0d5c02dbab49e8c19d98725c822f6fc409 |
| Linux | Linux Kernel | 4.12 up to, but not including, 4.14.276; 4.15 up to, but not including, 4.19.238; 4.20 up to, but not including, 5.4.189; 5.5 up to, but not including, 5.10.110; 5.11 up to, but not including, 5.15.33; 5.16 up to, but not including, 5.16.19; 5.17 up to, but not including, 5.17.1 | 4.14.276, 4.19.238, 5.4.189, 5.10.110, 5.15.33, 5.16.19 |
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 CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.0 | High | CNA |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: tpm: fix reference counting for struct tpm_chip The following sequence of operations results in a refcount warning: 1. Open device /dev/tpmrm. 2. Remove module tpm_tis_spi. 3. Write a TPM command to the file descriptor opened at step 1. ------------[ cut here ]------------ WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4 refcount_t: addition on 0; use-after-free. Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211 vc4 brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835] CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2 Hardware name: BCM2711 [<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14) [<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8) [<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108) [<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8) [<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>] (kobject_get+0xa0/0xa4) [<c08435d0>] (kobject_get) from [<bf0a715c>] (tpm_try_get_ops+0x14/0x54 [tpm]) [<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>] (tpm_common_write+0x38/0x60 [tpm]) [<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>] (vfs_write+0xc4/0x3c0) [<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc) [<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c) Exception stack(0xc226bfa8 to 0xc226bff0) bfa0: 00000000 000105b4 00000003 beafe664 00000014 00000000 bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000 beafe684 bfe0: 0000006c beafe648 0001056c b6eb6944 ---[ end trace d4b8409def9b8b1f ]--- The reason for this warning is the attempt to get the chip->dev reference in tpm_common_write() although the reference counter is already zero. Since commit 8979b02aaf1d ("tpm: Fix reference count to main device") the extra reference used to prevent a premature zero counter is never taken, because the required TPM_CHIP_FLAG_TPM2 flag is never set. Fix this by moving the TPM 2 character device handling from tpm_chip_alloc() to tpm_add_char_device() which is called at a later point in time when the flag has been set in case of TPM2. Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>") already introduced function tpm_devs_release() to release the extra reference but did not implement the required put on chip->devs that results in the call of this function. Fix this by putting chip->devs in tpm_chip_unregister(). Finally move the new implementation for the TPM 2 handling into a new function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the good case and error cases.
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.
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
Patches and release notes
- git.kernel.org/stable/c/290e05f346d1829e849662c97e42d5ad984f5258
- git.kernel.org/stable/c/2f928c0d5c02dbab49e8c19d98725c822f6fc409
- git.kernel.org/stable/c/473a66f99cb8173c14138c5a5c69bfad04e8f9ac
- git.kernel.org/stable/c/662893b4f6bd466ff9e1cd454c44c26d32d554fe
- git.kernel.org/stable/c/6e7baf84149fb43950631415de231b3a41915aa3
- git.kernel.org/stable/c/7e0438f83dc769465ee663bb5dcf8cc154940712
- git.kernel.org/stable/c/a27ed2f3695baf15f9b34d2d7a1f9fc105539a81
- git.kernel.org/stable/c/cb64bd038beacb4331fe464a36c8b5481e8f51e2
Recent Use After Free vulnerabilities
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