CVE-2023-52564: Revert "tty: n_gsm: fix UAF in gsm_cleanup_mux"
Vulnerability summary
CVE-2023-52564 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 16.4% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 5 · Related 5Timeline
- 02-03-2024PublishedVulnerability first disclosed.
- 23-05-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: Revert "tty: n_gsm: fix UAF in gsm_cleanup_mux" This reverts commit 9b9c8195f3f0d74a826077fc1c01b9ee74907239. The commit above is reverted as it did not solve the original issue. gsm_cleanup_mux() tries to free up the virtual ttys by calling gsm_dlci_release() for each available DLCI. There, dlci_put() is called to decrease the reference counter for the DLCI via tty_port_put() which finally calls gsm_dlci_free(). This already clears the pointer which is being checked in gsm_cleanup_mux() before calling gsm_dlci_release(). Therefore, it is not necessary to clear this pointer in gsm_cleanup_mux() as done in the reverted commit. The commit introduces a null pointer dereference: <TASK> ? __die+0x1f/0x70 ? page_fault_oops+0x156/0x420 ? search_exception_tables+0x37/0x50 ? fixup_exception+0x21/0x310 ? exc_page_fault+0x69/0x150 ? asm_exc_page_fault+0x26/0x30 ? tty_port_put+0x19/0xa0 gsmtty_cleanup+0x29/0x80 [n_gsm] release_one_tty+0x37/0xe0 process_one_work+0x1e6/0x3e0 worker_thread+0x4c/0x3d0 ? __pfx_worker_thread+0x10/0x10 kthread+0xe1/0x110 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x2f/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 </TASK> The actual issue is that nothing guards dlci_put() from being called multiple times while the tty driver was triggered but did not yet finished calling gsm_dlci_free().
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.25%
Chance of exploitation in the next 30 days
Percentile
16%
Versus all other CVEs
30-day change
Increase +0.01 pp
From 0.24% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu102 products
- linux< 5.15.0-94.104
- linux-allwinner-5.19All versions (No fix recorded)
- linux-aws< 5.15.0-1053.58
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 8fc0eabaa73bbd9bd705577071564616da5c8c61, < 6d5c8862932d31a810b6545f7d69ecc124402c6e | ≥ 5138c228311a863c3cf937b94a3ab4c87f1f70c4, < a48d2bcd23f2c98d575bc2f9b7a3fbd16aeea9eb | ≥ 9615ca54bc138e35353a001e8b5d4824dce72188, < c61d0b87a7028c2c10faffc524d748334c7b9827 | ≥ 9b9c8195f3f0d74a826077fc1c01b9ee74907239, < 2bff660e0ff349dee84dc4f6f6d10da4497f5b28 | ≥ 9b9c8195f3f0d74a826077fc1c01b9ee74907239, < 29346e217b8ab8a52889b88f00b268278d6b7668 | 74a8d6f50cc90ed0061997db51dfa81a62b0f835 | ≥ 5.10.190, < 5.10.198 | ≥ 5.15.124, < 5.15.134 | ≥ 6.1.43, < 6.1.56 | ≥ 6.4.8, < 6.5 | 6.5
- linux_kernel≥ 5.10.190, < 5.10.198 | ≥ 5.15.124, < 5.15.134 | ≥ 6.1.43, < 6.1.56 | ≥ 6.5, < 6.5.6 | 6.6:rc1 | 6.6:rc2 | 6.6:rc3
Debian1 product
- linux< 6.1.64-1 | < 6.5.6-1
3 vendors · 105 products
