Strix
56.1K

CVE-2026-72502

HIGHCVSS 7.5/10EPSS 0.21%

Last modified

CVE-2026-72502 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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".. EPSS estimates a 0.21% chance of exploitation in the next 30 days.

Description

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".

Metrics

CVSS 3.1
7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability
0.21%

11.6th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < 560b33b434e922ef97f9ff23aa2e909ef7aacd5c; >= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < 21f69ac1879bb970588d5e7c12a96e6542f7c1a7; >= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < c0db3dc2ac323b6c4b76adede3b355a9daa6dea8; >= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < 572fff10819dfc359298d1f774839e76a4d96f93; >= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < 8e6214a530c03e341dc1b0a846c8f2b716b3551a; >= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e; >= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < a210791f33345aa87187f7d7a9f3b9b7f4a28e6d; >= 3953c46c3ac7eef31a9935427371c6f54a22f1ba, < 2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22
LinuxLinux4.8

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is 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".
How severe is CVE-2026-72502?
CVE-2026-72502 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.21% probability of exploitation in the next 30 days.
How do I fix CVE-2026-72502?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

Related CVEs from 2026

View all 2026CVEs →

Are you affected by CVE-2026-72502?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST