CVE-2025-39964

crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

Published Oct 13, 2025 CVSS 3.1 · 7.8 High EPSS 1.6% KEV · Listed
Description
In the Linux kernel, the following vulnerability has been resolved:

crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg

Issuing two writes to the same af_alg socket is bogus as the
data will be interleaved in an unpredictable fashion. Furthermore,
concurrent writes may create inconsistencies in the internal
socket state.

Disallow this by adding a new ctx->write field that indiciates
exclusive ownership for writing.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4379-1 linux-6.1 security update
Debian DLA Debian DLA DLA-4404-1 linux security update
Debian DSA Debian DSA DSA-6053-1 linux security update
Ubuntu USN Ubuntu USN USN-7907-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7907-2 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7907-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7907-4 Linux kernel (GCP FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7921-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7922-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7922-2 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7928-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7928-2 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7928-3 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7907-5 Linux kernel kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7931-3 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7934-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-7935-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-7936-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-7937-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7938-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-7939-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-7939-2 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7940-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7921-2 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7922-3 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-7928-4 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-7931-4 Linux kernel (Xilinx) vulnerabilities
Ubuntu USN Ubuntu USN USN-7922-4 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-7928-5 Linux kernel (KVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-7931-5 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-7940-2 Linux kernel (Azure, N-Series) vulnerabilities
Ubuntu USN Ubuntu USN USN-7922-5 Linux kernel (IoT) vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'active', 'Technical Impact': 'total'}, 'version': '2.0.3'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Siemens
Siemens simatic S7-1500 Cpu 1518-4 Pn\/dp Mfp
Siemens simatic S7-1500 Cpu 1518-4 Pn\/dp Mfp Firmware
Siemens simatic S7-1500 Cpu 1518f-4 Pn\/dp Mfp
Siemens simatic S7-1500 Cpu 1518f-4 Pn\/dp Mfp Firmware
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:h:siemens:simatic_s7-1500_cpu_1518-4_pn\/dp_mfp:*:*:*:*:*:*:*:*
cpe:2.3:h:siemens:simatic_s7-1500_cpu_1518f-4_pn\/dp_mfp:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1518-4_pn\/dp_mfp_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_s7-1500_cpu_1518f-4_pn\/dp_mfp_firmware:*:*:*:*:*:*:*:*
Vendors & Products Siemens
Siemens simatic S7-1500 Cpu 1518-4 Pn\/dp Mfp
Siemens simatic S7-1500 Cpu 1518-4 Pn\/dp Mfp Firmware
Siemens simatic S7-1500 Cpu 1518f-4 Pn\/dp Mfp
Siemens simatic S7-1500 Cpu 1518f-4 Pn\/dp Mfp Firmware
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'active', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Metrics kev

{'dateAdded': '2026-09-18T00:00:00+00:00', 'dueDate': '2026-09-21T00:00:00+00:00'}

Type Values Removed Values Added
Weaknesses CWE-362
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 3.3, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 3.3, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'}

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Vendors & Products Linux
Linux linux Kernel
Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing.
Title crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg
References