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CVE-2026-63949— auxdisplay: line-display: fix OOB read on zero-length message_store()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 5.16版本存在安全漏洞，该漏洞源于在linedisp_display()函数中无条件读取msg[count - 1]前未检查count是否为零，导致零字节写入时出现越界读取，可能触发内核崩溃或读取相邻数据。

AI Predicted 7.8 Difficulty: Easy EPSS 0.21% · P12

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux 7e76aece6f036cb7ada4858d6aa73825bfe22983< ca5b0781946d5083ceafa752141f47f085853620 affected
7e76aece6f036cb7ada4858d6aa73825bfe22983< 8776032fe989a9b5fc77f2de5e03e4adb44c630e affected
7e76aece6f036cb7ada4858d6aa73825bfe22983< 3859960daeb9b7b39b9847b5b0113bc6081eb735 affected
7e76aece6f036cb7ada4858d6aa73825bfe22983< 197476b126010bac1b3199833c6966cd6f54c2a9 affected
7e76aece6f036cb7ada4858d6aa73825bfe22983< 6ad4f75ef9f3372fce8cad494e789ac6a5507bef affected
7e76aece6f036cb7ada4858d6aa73825bfe22983< a7511dcd9dd4bc55d123f9b800c8a4ed2662e5c6 affected
5.16 affected
< 5.16 unaffected
… +6 more rows
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I. Basic Information for CVE-2026-63949

Vulnerability Information
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Vulnerability Title
auxdisplay: line-display: fix OOB read on zero-length message_store()
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: auxdisplay: line-display: fix OOB read on zero-length message_store() linedisp_display() unconditionally reads msg[count - 1] before checking whether count is zero, so a write of zero bytes to the message sysfs attribute hits msg[-1]: write(fd, "", 0); -> message_store(..., buf, count=0) -> linedisp_display(linedisp, buf, count=0) -> msg[count - 1] == '\n' ; OOB read The kernfs write buffer for that store is a 1-byte allocation (kernfs_fop_write_iter() does kmalloc(len + 1) with len == 0), so msg[-1] is a 1-byte read before the slab object. On a KASAN-enabled kernel this trips an out-of-bounds report and panics; on stock kernels it silently reads adjacent slab data and, if that byte happens to be '\n', the following count-- wraps ssize_t 0 to -1 and is then passed to kmemdup_nul(). linedisp_display() is reached from the message_store() sysfs callback (drivers/auxdisplay/line-display.c message attribute, mode 0644) and from the in-tree initial-message setup with count == -1, so the OOB path is only userspace-triggerable via zero-byte writes; vfs_write() does not short-circuit on count == 0 and kernfs_fop_write_iter() dispatches the store callback regardless. Guard the trailing-newline trim with a count check. The existing if (!count) block then takes the clear-display path unchanged. Affects every auxdisplay driver that registers via linedisp_register() / linedisp_attach(): ht16k33, max6959, img-ascii-lcd, seg-led-gpio.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 5.16版本存在安全漏洞，该漏洞源于在linedisp_display()函数中无条件读取msg[count - 1]前未检查count是否为零，导致零字节写入时出现越界读取，可能触发内核崩溃或读取相邻数据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 7e76aece6f036cb7ada4858d6aa73825bfe22983 ~ ca5b0781946d5083ceafa752141f47f085853620 -
Linux Linux 5.16 -

II. Public POCs for CVE-2026-63949

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III. Intelligence Information for CVE-2026-63949

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Patches & Fixes for CVE-2026-63949 (6)

Same Patch Batch · Linux · 2026-07-19 · 429 CVEs total

CVE-2026-63795 10.0 CRITICAL 9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-64037 9.8 CRITICAL wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
CVE-2026-63993 9.8 CRITICAL vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
CVE-2026-63994 9.8 CRITICAL tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()
CVE-2026-64142 9.8 CRITICAL ksmbd: close durable scavenger races against m_fp_list lookups
CVE-2026-64000 9.8 CRITICAL net: hsr: fix potential OOB access in supervision frame handling
CVE-2026-64046 9.8 CRITICAL net: tls: prevent chain-after-chain in plain text SG
CVE-2026-64162 9.8 CRITICAL idpf: fix read_dev_clk_lock spinlock init in idpf_ptp_init()
CVE-2026-53399 9.8 CRITICAL nfsd: release layout stid on setlease failure
CVE-2026-53398 9.8 CRITICAL NFSD: Fix SECINFO_NO_NAME decode error cleanup
CVE-2026-64007 9.8 CRITICAL netfilter: synproxy: refresh tcphdr after skb_ensure_writable
CVE-2026-63825 9.8 CRITICAL gcov: use atomic counter updates to fix concurrent access crashes
CVE-2026-64016 9.8 CRITICAL ksmbd: fix durable reconnect error path file lifetime
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-63808 9.8 CRITICAL exfat: fix potential use-after-free in exfat_find_dir_entry()
CVE-2026-64025 9.8 CRITICAL bpf, skmsg: fix verdict sk_data_ready racing with ktls rx
CVE-2026-64125 9.8 CRITICAL net: bcmgenet: keep RBUF EEE/PM disabled
CVE-2026-64033 9.8 CRITICAL RDMA/rtrs: Fix use-after-free in path file creation cleanup
CVE-2026-64089 9.8 CRITICAL batman-adv: tt: fix negative last_changeset_len
CVE-2026-64035 9.8 CRITICAL igc: set tx buffer type for SMD frames

Showing top 20 of 429 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-63949

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