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CVE-2026-31415 medium CVSS 5.5

Vulnerability in Linux kernel (CVE-2026-31415)

Summary

Vulnerability in Linux kernel (CVE-2026-31415). Risk of unauthorized operations or information disclosure. Exploitable via __u16.

Original description

The description as published by the source.

In the Linux kernel, the following vulnerability has been resolved:

ipv6: avoid overflows in ip6_datagram_send_ctl()

Yiming Qian reported :

I believe I found a locally triggerable kernel bug in the IPv6 sendmsg
ancillary-data path that can panic the kernel via skb_under_panic()
(local DoS).

The core issue is a mismatch between:

  • a 16-bit length accumulator (struct ipv6_txoptions::opt_flen, type
    __u16) and
  • a pointer to the last provided destination-options header (opt->dst1opt)

when multiple IPV6_DSTOPTS control messages (cmsgs) are provided.

  • include/net/ipv6.h:
    • struct ipv6_txoptions::opt_flen is __u16 (wrap possible).
      (lines 291-307, especially 298)
  • net/ipv6/datagram.c:ip6_datagram_send_ctl():
    • Accepts repeated IPV6_DSTOPTS and accumulates into opt_flen
      without rejecting duplicates. (lines 909-933)
  • net/ipv6/ip6_output.c:__ip6_append_data():
    • Uses opt->opt_flen + opt->opt_nflen to compute header
      sizes/headroom decisions. (lines 1448-1466, especially 1463-1465)
  • net/ipv6/ip6_output.c:__ip6_make_skb():
    • Calls ipv6_push_frag_opts() if opt->opt_flen is non-zero.
      (lines 1930-1934)
  • net/ipv6/exthdrs.c:ipv6_push_frag_opts() / ipv6_push_exthdr():
    • Push size comes from ipv6_optlen(opt->dst1opt) (based on the
      pointed-to header). (lines 1179-1185 and 1206-1211)
  1. opt_flen is a 16-bit accumulator:
  • include/net/ipv6.h:298 defines __u16 opt_flen; /* after fragment hdr */.
  1. `ip6_d…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-31415 has been found in Linux kernel.
Attackers can target a specific entry point like __u16 over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-31415" on the vendor's site.

CVE-2026-31415 (Linux kernel) — CWE-617 / CVSS v3 5.5
Attack vector: local / no user interaction
Attack surface: __u16 / IPV6_DSTOPTS / opt_flen / CAP_NET_RAW
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-617) exists in Linux kernel. Attackers reach the vulnerable code path via __u16.

📍 Affected scope

Check the vendor advisory for the affected versions of Linux kernel. Attack surface: __u16 / IPV6_DSTOPTS / opt_flen / CAP_NET_RAW.

🔥 Severity

Severity: Medium (CVSS 5.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Linux Kernel
[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.14"},{"fixed":"5.10.253"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.203"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.168"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.134"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.81"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.22"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.12"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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