Linux Kernel up to 6.6.98/6.12.38/6.15.6/6.16-rc5 tcp tcp_bound_to_half_wnd involved allocation of resources

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5.4$0-$5k0.00

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.6.98/6.12.38/6.15.6/6.16-rc5 and classified as problematic. Affected by this issue is the function tcp_bound_to_half_wnd of the component tcp. The manipulation of the argument involved leads to allocation of resources. This vulnerability is uniquely identified as CVE-2025-38463. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 6.6.98/6.12.38/6.15.6/6.16-rc5. This issue affects the function tcp_bound_to_half_wnd of the component tcp. The manipulation of the argument involved with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. The impact remains unknown. The summary by CVE is:

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

It is possible to read the advisory at git.kernel.org. The identification of this vulnerability is CVE-2025-38463 since 04/16/2025. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 253428 (SUSE SLES15 Security Update : kernel (SUSE-SU-2025:02923-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.99, 6.12.39, 6.15.7 or 6.16-rc6 eliminates this vulnerability. Applying the patch 81373cd1d72d87c7d844d4454a526b8f53e72d00/62e6160cfb5514787bda833d466509edc38fde23/9f164fa6bb09fbcc60fa5c3ff551ce9eec1befd7/d3a5f2871adc0c61c61869f37f3e697d97f03d8c is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (253428), EUVD (EUVD-2025-22678) and CERT Bund (WID-SEC-2025-1653). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • IBM QRadar SIEM
  • SUSE openSUSE
  • RESF Rocky Linux
  • Dell Avamar
  • Open Source Linux Kernel
  • Dell NetWorker
  • Dell Secure Connect Gateway

Productinfo

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Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Allocation of resources
CWE: CWE-770 / CWE-400 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 253428
Nessus Name: SUSE SLES15 Security Update : kernel (SUSE-SU-2025:02923-1)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.6.99/6.12.39/6.15.7/6.16-rc6
Patch: 81373cd1d72d87c7d844d4454a526b8f53e72d00/62e6160cfb5514787bda833d466509edc38fde23/9f164fa6bb09fbcc60fa5c3ff551ce9eec1befd7/d3a5f2871adc0c61c61869f37f3e697d97f03d8c

Timelineinfo

04/16/2025 CVE reserved
07/25/2025 +100 days Advisory disclosed
07/25/2025 +0 days VulDB entry created
01/04/2026 +162 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-38463 (🔒)
GCVE (CVE): GCVE-0-2025-38463
GCVE (VulDB): GCVE-100-317747
EUVD: 🔒
CERT Bund: WID-SEC-2025-1653 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 07/25/2025 19:32
Updated: 01/04/2026 00:15
Changes: 07/25/2025 19:32 (59), 07/28/2025 07:58 (1), 07/30/2025 04:17 (1), 08/22/2025 22:44 (7), 08/24/2025 02:12 (2), 09/15/2025 05:37 (1), 09/29/2025 02:26 (1), 11/02/2025 13:58 (1), 11/20/2025 03:31 (10), 01/04/2026 00:15 (1)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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