The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applicationsUpgrade Amazon-Linux:2023 kernel6.12-modules-extra to version 1:6.12.113-138.209.amzn2023 or higher.
This issue was patched in ALAS2023-2026-3335.
Note: Versions mentioned in the description apply only to the upstream kernel6.12-modules-extra package and not the kernel6.12-modules-extra package as distributed by Amazon-Linux.
See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
ipv4: stop PMTU walk when nexthop group shrinks
Commit 7d3f3b4367f3 ("net: ipv4: Cache pmtu for all packet paths if multipath enabled") made __ip_rt_update_pmtu() update every path.
For nexthop objects, fib_info_num_path() and fib_info_nhc() independently load nh->nh_grp. RCU protects each group's lifetime but does not make the loads observe the same group. If replacement shrinks the group after the loop accepts an index, fib_info_nhc() returns NULL and update_or_create_fnhe() dereferences it.
A deterministic probe only widened the existing window between the real operations. On v7.2, an RTM_NEWNEXTHOP replacement published a one-member group after the PMTU reader accepted index 1 from a two-member group, producing:
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: update_or_create_fnhe+0x45/0x15b0
Stop when the indexed path is absent. Groups are dense, so no later index exists in that snapshot. The same real-writer window completed 114,423 PMTU iterations without an oops with this check. A reproducer is available on request.
Replacement requires CAP_NET_ADMIN in the network namespace. Where unprivileged user namespaces are permitted, a local user can obtain it in a new user and network namespace.