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CVE-2026-31610— ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc

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SPNEGO解码失败后mechToken泄漏，因为分配后解码错误导致清理条件不满足。

AI Predicted 5.3 Difficulty: Moderate EPSS 0.14% · P3

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux fad4161b5cd01a24202234976ebbb133f7adc0b5< ae9cdb29efed20ffdee9ff3b0bb72fb369c353da affected
fad4161b5cd01a24202234976ebbb133f7adc0b5< bd4a7fb04f06f419b0e93d8b52fe32067eb312d1 affected
fad4161b5cd01a24202234976ebbb133f7adc0b5< 745a535461bbb90a56d9357573c9f97a5c12abe1 affected
fad4161b5cd01a24202234976ebbb133f7adc0b5< dd577cb55588ec3fbc66af3621280306601c4192 affected
fad4161b5cd01a24202234976ebbb133f7adc0b5< dd53414e301beb915fe672dc4c4a51bafb917604 affected
fad4161b5cd01a24202234976ebbb133f7adc0b5< 269c800a7a7e363459291885b35f7bc72e231ed6 affected
fad4161b5cd01a24202234976ebbb133f7adc0b5< 6c8c44e6553b9f072f62d9875e567766eb293162 affected
fad4161b5cd01a24202234976ebbb133f7adc0b5< ad0057fb91218914d6c98268718ceb9d59b388e1 affected
… +10 more rows
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I. Basic Information for CVE-2026-31610

Vulnerability Information
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Vulnerability Title
ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc The kernel ASN.1 BER decoder calls action callbacks incrementally as it walks the input. When ksmbd_decode_negTokenInit() reaches the mechToken [2] OCTET STRING element, ksmbd_neg_token_alloc() allocates conn->mechToken immediately via kmemdup_nul(). If a later element in the same blob is malformed, then the decoder will return nonzero after the allocation is already live. This could happen if mechListMIC [3] overrunse the enclosing SEQUENCE. decode_negotiation_token() then sets conn->use_spnego = false because both the negTokenInit and negTokenTarg grammars failed. The cleanup at the bottom of smb2_sess_setup() is gated on use_spnego: if (conn->use_spnego && conn->mechToken) { kfree(conn->mechToken); conn->mechToken = NULL; } so the kfree is skipped, causing the mechToken to never be freed. This codepath is reachable pre-authentication, so untrusted clients can cause slow memory leaks on a server without even being properly authenticated. Fix this up by not checking check for use_spnego, as it's not required, so the memory will always be properly freed. At the same time, always free the memory in ksmbd_conn_free() incase some other failure path forgot to free it.
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SPNEGO解码失败后mechToken泄漏，因为分配后解码错误导致清理条件不满足。
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 fad4161b5cd01a24202234976ebbb133f7adc0b5 ~ ae9cdb29efed20ffdee9ff3b0bb72fb369c353da -
Linux Linux 5.15 -

II. Public POCs for CVE-2026-31610

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III. Intelligence Information for CVE-2026-31610

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Patches & Fixes for CVE-2026-31610 (4)

Same Patch Batch · Linux · 2026-04-24 · 138 CVEs total

CVE-2026-31649 9.8 CRITICAL net: stmmac: fix integer underflow in chain mode
CVE-2026-31607 9.8 CRITICAL usbip: validate number_of_packets in usbip_pack_ret_submit()
CVE-2026-31633 9.8 CRITICAL rxrpc: Fix integer overflow in rxgk_verify_response()
CVE-2026-31608 9.8 CRITICAL smb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list
CVE-2026-31669 9.8 CRITICAL mptcp: fix slab-use-after-free in __inet_lookup_established
CVE-2026-31668 9.8 CRITICAL seg6: separate dst_cache for input and output paths in seg6 lwtunnel
CVE-2026-31589 9.8 CRITICAL mm: call ->free_folio() directly in folio_unmap_invalidate()
CVE-2026-31609 9.8 CRITICAL smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()
CVE-2026-31536 9.8 CRITICAL smb: server: let send_done handle a completion without IB_SEND_SIGNALED
CVE-2026-31657 9.8 CRITICAL batman-adv: hold claim backbone gateways by reference
CVE-2026-31637 9.8 CRITICAL rxrpc: reject undecryptable rxkad response tickets
CVE-2026-31659 9.8 CRITICAL batman-adv: reject oversized global TT response buffers
CVE-2026-31636 9.1 CRITICAL rxrpc: fix RESPONSE authenticator parser OOB read
CVE-2026-31629 8.8 HIGH nfc: llcp: add missing return after LLCP_CLOSED checks
CVE-2026-31570 8.8 HIGH can: gw: fix OOB heap access in cgw_csum_crc8_rel()
CVE-2026-31558 8.8 HIGH LoongArch: KVM: Make kvm_get_vcpu_by_cpuid() more robust
CVE-2026-31553 8.8 HIGH KVM: arm64: Fix the descriptor address in __kvm_at_swap_desc()
CVE-2026-31622 8.8 HIGH NFC: digital: Bounds check NFC-A cascade depth in SDD response handler
CVE-2026-31588 8.8 HIGH KVM: x86: Use scratch field in MMIO fragment to hold small write values
CVE-2026-31611 8.6 HIGH ksmbd: require 3 sub-authorities before reading sub_auth[2]

Showing top 20 of 138 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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