LiveActive security incident?Get immediate response
CVE Record

CVE-2025-39913: tcp_bpf: Call sk_msg_free() when tcp_bpf_send_verdict() fails to allocate psock->cork.

In the Linux kernel, the following vulnerability has been resolved: tcp_bpf: Call sk_msg_free() when tcp_bpf_send_verdict() fails to allocate psock->cork. syzbot reported the splat below. [0] The repro does the following: 1. Load a sk_msg prog that calls bpf_msg_cork_bytes(msg, cork_bytes) 2. Attach the prog to a SOCKMAP 3. Add a socket to the SOCKMAP 4. Activate fault injection 5. Send data less than cork_bytes At 5., the data is carried over to the next sendmsg() as it is smaller than the cork_bytes specified by bpf_msg_cork_bytes(). Then, tcp_bpf_send_verdict() tries to allocate psock->cork to hold the data, but this fails silently due to fault injection + __GFP_NOWARN. If the allocation fails, we need to revert the sk->sk_forward_alloc change done by sk_msg_alloc(). Let's call sk_msg_free() when tcp_bpf_send_verdict fails to allocate psock->cork. The "*copied" also needs to be updated such that a proper error can be returned to the caller, sendmsg. It fails to allocate psock->cork. Nothing has been corked so far, so this patch simply sets "*copied" to 0. [0]: WARNING: net/ipv4/af_inet.c:156 at inet_sock_destruct+0x623/0x730 net/ipv4/af_inet.c:156, CPU#1: syz-executor/5983 Modules linked in: CPU: 1 UID: 0 PID: 5983 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:inet_sock_destruct+0x623/0x730 net/ipv4/af_inet.c:156 Code: 0f 0b 90 e9 62 fe ff ff e8 7a db b5 f7 90 0f 0b 90 e9 95 fe ff ff e8 6c db b5 f7 90 0f 0b 90 e9 bb fe ff ff e8 5e db b5 f7 90 <0f> 0b 90 e9 e1 fe ff ff 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c 9f fc RSP: 0018:ffffc90000a08b48 EFLAGS: 00010246 RAX: ffffffff8a09d0b2 RBX: dffffc0000000000 RCX: ffff888024a23c80 RDX: 0000000000000100 RSI: 0000000000000fff RDI: 0000000000000000 RBP: 0000000000000fff R08: ffff88807e07c627 R09: 1ffff1100fc0f8c4 R10: dffffc0000000000 R11: ffffed100fc0f8c5 R12: ffff88807e07c380 R13: dffffc0000000000 R14: ffff88807e07c60c R15: 1ffff1100fc0f872 FS: 00005555604c4500(0000) GS:ffff888125af1000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005555604df5c8 CR3: 0000000032b06000 CR4: 00000000003526f0 Call Trace: <IRQ> __sk_destruct+0x86/0x660 net/core/sock.c:2339 rcu_do_batch kernel/rcu/tree.c:2605 [inline] rcu_core+0xca8/0x1770 kernel/rcu/tree.c:2861 handle_softirqs+0x286/0x870 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline] invoke_softirq kernel/softirq.c:453 [inline] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1052 </IRQ>

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2025-39913 is a Linux kernel bug in tcp_bpf handling. Under a failed allocation while BPF message corking is used, kernel socket accounting is not unwound correctly. The public evidence shows a syzbot-triggered kernel warning, not confirmed real-world compromise.

Executive priority

Treat as a scheduled kernel update item, elevated for multi-tenant Linux hosts, container platforms, or products exposing BPF-capable local users. Current sources do not justify emergency response absent vendor-specific severity guidance.

Technical view

In tcp_bpf_send_verdict(), allocation failure for psock->cork after sk_msg_alloc() could leave sk->sk_forward_alloc accounting changed. The fix calls sk_msg_free() and resets copied to 0 so sendmsg receives a proper error. The reproducer uses sk_msg BPF, SOCKMAP, corking, and fault injection.

Likely exposure

Exposure is most plausible on Linux systems running affected kernel builds with BPF SOCKMAP/sk_msg functionality reachable by users or workloads with sufficient privileges. The bundle lists Linux as affected and includes stable kernel fix commits plus Debian LTS and Siemens advisories.

Exploitation context

The bundle does not show KEV listing or active exploitation. The described trigger is from syzbot and depends on a specific BPF/SOCKMAP setup plus allocation failure. Public evidence supports a kernel reliability/accounting flaw, but not a broadly exploited remote attack.

Researcher notes

Evidence is strongest for a fault-injection-discovered kernel bug with a narrow trigger path. No CVSS, CWE, or exploit-in-the-wild evidence is provided. Validate downstream kernel backports rather than relying only on upstream version numbers.

Mitigation direction

  • Apply vendor or distribution kernel updates containing the referenced Linux stable fixes.
  • Review Debian LTS and Siemens advisories if those platforms are in scope.
  • Prioritize systems where untrusted users or workloads can use BPF-related features.
  • Check vendor guidance before applying any workaround not documented by your distribution.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and embedded products.
  • Map deployed versions against vendor advisories and the CVE affected-version data.
  • Confirm updated kernels include one of the referenced stable commits or downstream backports.
  • Check whether BPF SOCKMAP/sk_msg functionality is exposed to untrusted local workloads.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2025-39913 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
3ADP providers
11Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
siemens-SADPADP container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux4f738adba30a7cfc006f605707e7aee847ffefa0, 4f738adba30a7cfc006f605707e7aee847ffefa0, 4f738adba30a7cfc006f605707e7aee847ffefa0, 4f738adba30a7cfc006f605707e7aee847ffefa0, 4f738adba30a7cfc006f605707e7aee847ffefa0, 4f738adba30a7cfc006f605707e7aee847ffefa0, 4f738adba30a7cfc006f605707e7aee847ffefa0, 4f738adba30a7cfc006f605707e7aee847ffefa0unaffected
LinuxLinux4.17, 0, 5.4.300, 5.10.245, 5.15.194, 6.1.153, 6.6.107, 6.12.48, 6.16.8, 6.17affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.