Linux: Use After Free
CVE-2023-53536 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 701a8220762ff90615dc91d3543f789391b63298, 5bb4005fb667c6e2188fa87950f8d5faf2994410, 64ef787bb1588475163069c2e62fdd8f6c27b1f6 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 0.16% 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 701a8220762ff90615dc91d3543f789391b63298 or 5bb4005fb667c6e2188fa87950f8d5faf2994410 or 64ef787bb1588475163069c2e62fdd8f6c27b1f6 or 809a5be62e92a444a3c3d7b9f438019d0b322f55, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.180 or 5.15.111 or 6.1.28 or 6.2.15, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 1b2628397058ebce7277480960b29c788138de90 up to, but not including, 701a8220762ff90615dc91d3543f789391b63298; 1b2628397058ebce7277480960b29c788138de90 up to, but not including, 5bb4005fb667c6e2188fa87950f8d5faf2994410; 1b2628397058ebce7277480960b29c788138de90 up to, but not including, 64ef787bb1588475163069c2e62fdd8f6c27b1f6; 1b2628397058ebce7277480960b29c788138de90 up to, but not including, 809a5be62e92a444a3c3d7b9f438019d0b322f55; 1b2628397058ebce7277480960b29c788138de90 up to, but not including, 5c62852942667c613de0458fc797c5b8c36112b5; 1b2628397058ebce7277480960b29c788138de90 up to, but not including, 5c7cb94452901a93e90c2230632e2c12a681bc92; 5.8 | 701a8220762ff90615dc91d3543f789391b63298, 5bb4005fb667c6e2188fa87950f8d5faf2994410, 64ef787bb1588475163069c2e62fdd8f6c27b1f6, 809a5be62e92a444a3c3d7b9f438019d0b322f55, 5c62852942667c613de0458fc797c5b8c36112b5, 5c7cb94452901a93e90c2230632e2c12a681bc92 |
| Linux | Linux Kernel | 5.8 up to, but not including, 5.10.180; 5.11 up to, but not including, 5.15.111; 5.16 up to, but not including, 6.1.28; 6.2 up to, but not including, 6.2.15; 6.3 up to, but not including, 6.3.2 | 5.10.180, 5.15.111, 6.1.28, 6.2.15, 6.3.2 |
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.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: blk-crypto: make blk_crypto_evict_key() more robust If blk_crypto_evict_key() sees that the key is still in-use (due to a bug) or that ->keyslot_evict failed, it currently just returns while leaving the key linked into the keyslot management structures. However, blk_crypto_evict_key() is only called in contexts such as inode eviction where failure is not an option. So actually the caller proceeds with freeing the blk_crypto_key regardless of the return value of blk_crypto_evict_key(). These two assumptions don't match, and the result is that there can be a use-after-free in blk_crypto_reprogram_all_keys() after one of these errors occurs. (Note, these errors *shouldn't* happen; we're just talking about what happens if they do anyway.) Fix this by making blk_crypto_evict_key() unlink the key from the keyslot management structures even on failure. Also improve some comments.
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/5bb4005fb667c6e2188fa87950f8d5faf2994410
- git.kernel.org/stable/c/5c62852942667c613de0458fc797c5b8c36112b5
- git.kernel.org/stable/c/5c7cb94452901a93e90c2230632e2c12a681bc92
- git.kernel.org/stable/c/64ef787bb1588475163069c2e62fdd8f6c27b1f6
- git.kernel.org/stable/c/701a8220762ff90615dc91d3543f789391b63298
- git.kernel.org/stable/c/809a5be62e92a444a3c3d7b9f438019d0b322f55
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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