CVE-2026-72502

In the Linux kernel, the following vulnerability has been resolved: tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF) When MTU is large, ip6_default_advmss() can return IPV6_MAXPLEN (65535). This is interpreted by TCP as mss_clamp, allowing the MSS to reach 65535. However, 0xFFFF is also used as a magic value GSO_BY_FRAGS in the kernel. If a TCP packet with gso_size=0xFFFF is passed to skb_segment(), it will be mistakenly treated as GSO_BY_FRAGS, leading to a NULL pointer dereference because local TCP packets do not use frag_list. Fix this by returning min(IPV6_MAXPLEN, GSO_BY_FRAGS - 1) (65534) from ip6_default_advmss() when MTU is large. Also update the stale comment in ip6_default_advmss() which suggested that IPV6_MAXPLEN is returned to mean "any MSS".

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://git.kernel.org/stable/c/21f69ac1879bb970588d5e7c12a96e6542f7c1a7
https://git.kernel.org/stable/c/2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22
https://git.kernel.org/stable/c/560b33b434e922ef97f9ff23aa2e909ef7aacd5c
https://git.kernel.org/stable/c/572fff10819dfc359298d1f774839e76a4d96f93
https://git.kernel.org/stable/c/8e6214a530c03e341dc1b0a846c8f2b716b3551a
https://git.kernel.org/stable/c/a210791f33345aa87187f7d7a9f3b9b7f4a28e6d
https://git.kernel.org/stable/c/c0db3dc2ac323b6c4b76adede3b355a9daa6dea8
https://git.kernel.org/stable/c/d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e

Configurations

No configuration.

History

No history.

Information

Published : 2026-08-15 06:22

Updated : 2026-08-17 06:19

NVD link : CVE-2026-72502

Mitre link : CVE-2026-72502

CVE.ORG link : CVE-2026-72502

JSON object : View

Products Affected

No product.

CWE

No CWE.

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"https://git.kernel.org/stable/c/a210791f33345aa87187f7d7a9f3b9b7f4a28e6d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/c0db3dc2ac323b6c4b76adede3b355a9daa6dea8", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "vulnStatus": "Received", "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)\n\nWhen MTU is large, ip6_default_advmss() can return IPV6_MAXPLEN (65535).\nThis is interpreted by TCP as mss_clamp, allowing the MSS to reach 65535.\n\nHowever, 0xFFFF is also used as a magic value GSO_BY_FRAGS in the kernel.\nIf a TCP packet with gso_size=0xFFFF is passed to skb_segment(), it will\nbe mistakenly treated as GSO_BY_FRAGS, leading to a NULL pointer\ndereference because local TCP packets do not use frag_list.\n\nFix this by returning min(IPV6_MAXPLEN, GSO_BY_FRAGS - 1) (65534) from\nip6_default_advmss() when MTU is large.\n\nAlso update the stale comment in ip6_default_advmss() which suggested\nthat IPV6_MAXPLEN is returned to mean \"any MSS\"."}], "lastModified": "2026-08-17T06:19:18.647", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}