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CVE-2025-38463— tcp: Correct signedness in skb remaining space calculation

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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于skb剩余空间计算中的符号错误，可能导致缓冲区溢出。

CVSS 7.8 · High EPSS 0.18% · P7

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux 270a1c3de47e49dd2fc18f48e46b101e48050e78< 81373cd1d72d87c7d844d4454a526b8f53e72d00 affected
270a1c3de47e49dd2fc18f48e46b101e48050e78< 62e6160cfb5514787bda833d466509edc38fde23 affected
270a1c3de47e49dd2fc18f48e46b101e48050e78< 9f164fa6bb09fbcc60fa5c3ff551ce9eec1befd7 affected
270a1c3de47e49dd2fc18f48e46b101e48050e78< d3a5f2871adc0c61c61869f37f3e697d97f03d8c affected
6.5 affected
< 6.5 unaffected
6.6.99≤ 6.6.* unaffected
6.12.39≤ 6.12.* unaffected
… +2 more rows
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I. Basic Information for CVE-2025-38463

Vulnerability Information
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Vulnerability Title
tcp: Correct signedness in skb remaining space calculation
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: tcp: Correct signedness in skb remaining space calculation Syzkaller reported a bug [1] where sk->sk_forward_alloc can overflow. When we send data, if an skb exists at the tail of the write queue, the kernel will attempt to append the new data to that skb. However, the code that checks for available space in the skb is flawed: ''' copy = size_goal - skb->len ''' The types of the variables involved are: ''' copy: ssize_t (s64 on 64-bit systems) size_goal: int skb->len: unsigned int ''' Due to C's type promotion rules, the signed size_goal is converted to an unsigned int to match skb->len before the subtraction. The result is an unsigned int. When this unsigned int result is then assigned to the s64 copy variable, it is zero-extended, preserving its non-negative value. Consequently, copy is always >= 0. Assume we are sending 2GB of data and size_goal has been adjusted to a value smaller than skb->len. The subtraction will result in copy holding a very large positive integer. In the subsequent logic, this large value is used to update sk->sk_forward_alloc, which can easily cause it to overflow. The syzkaller reproducer uses TCP_REPAIR to reliably create this condition. However, this can also occur in real-world scenarios. The tcp_bound_to_half_wnd() function can also reduce size_goal to a small value. This would cause the subsequent tcp_wmem_schedule() to set sk->sk_forward_alloc to a value close to INT_MAX. Further memory allocation requests would then cause sk_forward_alloc to wrap around and become negative. [1]: https://syzkaller.appspot.com/bug?extid=de6565462ab540f50e47
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于skb剩余空间计算中的符号错误，可能导致缓冲区溢出。
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 270a1c3de47e49dd2fc18f48e46b101e48050e78 ~ 81373cd1d72d87c7d844d4454a526b8f53e72d00 -
Linux Linux 6.5 -

II. Public POCs for CVE-2025-38463

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III. Intelligence Information for CVE-2025-38463

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Same Patch Batch · Linux · 2025-07-25 · 114 CVEs total

CVE-2025-38429 10.0 CRITICAL bus: mhi: ep: Update read pointer only after buffer is written
CVE-2025-38411 9.8 CRITICAL netfs: Fix double put of request
CVE-2025-38430 9.8 CRITICAL nfsd: nfsd4_spo_must_allow() must check this is a v4 compound request
CVE-2025-38439 9.8 CRITICAL bnxt_en: Set DMA unmap len correctly for XDP_REDIRECT
CVE-2025-38365 9.1 CRITICAL btrfs: fix a race between renames and directory logging
CVE-2025-38377 8.8 HIGH rose: fix dangling neighbour pointers in rose_rt_device_down()
CVE-2025-38367 8.8 HIGH LoongArch: KVM: Avoid overflow with array index
CVE-2025-38437 8.8 HIGH ksmbd: fix potential use-after-free in oplock/lease break ack
CVE-2025-38375 8.4 HIGH virtio-net: ensure the received length does not exceed allocated size
CVE-2025-38395 8.4 HIGH regulator: gpio: Fix the out-of-bounds access to drvdata::gpiods
CVE-2025-38386 7.8 HIGH ACPICA: Refuse to evaluate a method if arguments are missing
CVE-2025-38449 7.8 HIGH drm/gem: Acquire references on GEM handles for framebuffers
CVE-2025-38434 7.8 HIGH Revert "riscv: Define TASK_SIZE_MAX for __access_ok()"
CVE-2025-38412 7.8 HIGH platform/x86: dell-wmi-sysman: Fix WMI data block retrieval in sysfs callbacks
CVE-2025-38382 7.8 HIGH btrfs: fix iteration of extrefs during log replay
CVE-2025-38447 7.8 HIGH mm/rmap: fix potential out-of-bounds page table access during batched unmap
CVE-2025-38398 7.8 HIGH spi: spi-qpic-snand: reallocate BAM transactions
CVE-2025-38408 7.8 HIGH genirq/irq_sim: Initialize work context pointers properly
CVE-2025-38396 7.8 HIGH fs: export anon_inode_make_secure_inode() and fix secretmem LSM bypass
CVE-2025-38435 7.8 HIGH riscv: vector: Fix context save/restore with xtheadvector

Showing top 20 of 114 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-38463

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